Tutorial Blog

Function and Procedure

2010-08-03T20:16:00.000-07:00

There are two kind of subroutine in Pascal : Function and Procedure. The difference between these subroutines is in return value. Function gives a return value, but procedure doesn’t. The structure of function and procedure are the same :

Here is the example of procedure and function :

program FunctionAndProcedure;
{$APPTYPE CONSOLE}
uses
SysUtils;

procedure Add1(x, y : integer);
var
z : integer;
begin
z := x + y;
writeln(x,' + ',y,' = ',z,' (using procedure)');
readln;
end;

function Add2(x, y : integer) : integer;
begin
Add2 := x + y;
end;

begin
Add1(25,10);
writeln('25 + 40 = ',Add2(25,40),' (using function)');
readln;
end.

You can download the complete code here.

The Complete Electronic Circuit

2010-07-27T20:54:00.000-07:00

(Dancing Lamp #3)

In my previous tutorial, I’ve given you the example program and the LED circuit. But what you’ve got is only a small electronic circuit on your table. How about if you want to use bigger light bulbs instead of using LED. Here is the complete electronic circuit :

You have to connect parallel port ground pin out to the circuit ground. Just be careful while connecting this circuit to your computer, or it will damage your computer !!! Make sure that everything is in the place.

Using this circuit, if you send a “high” to the data pin out (D0 .. D7), it will trigger the transistor. It will be saturated, and let current flows through the relay and the light bulb will be connected to the electricity and light on. Use this circuit for each data pin out of your parallel port.

Previous tutorials about dancing lamp :

Accessing your PC’s parallel port using Inpout32.dll in Delphi

LED Circuit

2010-07-26T19:00:00.000-07:00

(Dancing Lamp # 2)

To test the program I’ve created in my previous tutorial, I use this circuit (see picture). But be careful while you connect this circuit to your parallel port. Make sure that every component is in the right place or connection, otherwise it will damage your PC !!!

I use 1 KOhm resistors. If you send an integer data = 15 to the parallel port, D0…D3 LED will be light on. And D4…D7 LED will be off.

You can arrange which LED is on or off by writing some codes in Delphi. And you can also set the delay of each step you turn on or off the LED using OnTimer event of Timer component in Delphi. I’ve created an example program for you.

Download the example program here.

Go to previous tutorial (Accessing your PC’s parallel port using Inpout32.dll in Delphi)

Go to next tutorial (The Complete Electronic Circuit)

Accessing your PC’s parallel port using Inpout32.dll in Delphi

2010-07-19T21:01:00.000-07:00

(Dancing Lamp # 1)

Before we create a dancing lamp using our PC’s parallel port, we have to know the parallel port female pin-out (see the picture below).

D0 is the LSB (Least Significant Bit) and D7 is the Most Significant Bit (MSB). You can send an integer type data to the D0..D7 pin-outs. And the output will be the binary form of the integer we send. For example : If we send an integer data 15 the output will be :

D7	D6	D5	D4	D3	D2	D1	D0
LOW	LOW	LOW	LOW	HIGH	HIGH	HIGH	HIGH

15 (byte) = 00001111 (binary)

How To Send Data To The Parallel Port ?

To send data to the parallel port I use a DLL file (Inpout32.dll) that can be downloaded at logix4u.net, and it’s free for non-commercial manner. Place this file in C:\WINDOWS\system or in the same folder with you project you’re going to create.

To use this file you can see my previous tutorial about using a DLL file. This DLL file contains a function called Out32(). The syntax of this function :

Out32(portaddress,data);

Usually, the port address is $378 (you can check the BIOS setting of your PC)

Example program :

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;

type
TForm1 = class(TForm)
Edit1: TEdit;
Label1: TLabel;
Button1: TButton;
procedure FormActivate(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.DFM}
function Out32(wAddr:word;bOut:byte):byte; stdcall; external 'inpout32.dll';

procedure TForm1.FormActivate(Sender: TObject);
begin
Edit1.Text := '';
Edit1.SetFocus;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
Out32($378,StrToInt(Edit1.Text));
end;

end.

You can download the complete code here.

Go to next tutorial (LED Circuit)

Pointer

2010-07-07T23:10:00.000-07:00

Pointer is a variable that points toward a memory address. So a pointer is a data address. The data is somewhere else. Below picture will show you the relationship between a pointer and a data pointed by a pointer.

To declare a pointer, use the below statement :

Type

PointerType : ^Type;

In this case, type can be an integer, a real, an array or record. And you can see the example code of using a pointer :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

type
PointerType = ^integer;

var
MyPointer : PointerType;
Data : integer;

begin
Data := 100;
MyPointer := @Data;
writeln('Data pointed toward by the pointer is ', MyPointer^);
Data := 123;
writeln('Data pointed toward by the pointer is ', MyPointer^);
readln;
end.

Disposing pointer allocation

To free the memory that is used by a pointer, you can use dispose statement.

Dispose(pointer);

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
MyPointer : ^integer;

begin
New(MyPointer); // allocate memory
MyPointer^ := 100;
writeln('Vallue pointed toward by MyPointer is ',MyPointer^);
Dispose(MyPointer); // free memory allocation
readln;
end.

You can download the complete code here.

Record’s variant

2010-06-20T20:05:00.000-07:00

A record can have one or more variant elements or fields. This variant allows data to accessed using one or more different fields. To declare a record contain variant use these statements :

Type

RecordTypeName = record

Field_1 : type_1;

Field_n : type_n;

Case Tag : OrdinalType of

Constant_1 : ( variant_1);

Constant_2 : ( variant_2);

End;

Example record contain variant :

Type

TCategory = (FullTimer, PartTimer);

TEmployeeRecord : record

Name : String(30);

Case Category : TCategory of

Full Time : ( Salary : currency;

Bonus : currency);

Part Time : ( Salary : currency);

End;

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

type
TCategory = ( FullTimer, PartTimer );
TEmployeeRecord = record
Name : String[30];
Case Category : TCategory of
FullTimer : ( Salary : currency;
Bonus : currency);
PartTimer : ( Payment : currency);
end;

var
Employee : TEmployeeRecord;

begin
with Employee do
begin
// assigning fields' values
Name := 'Albert Einstein';
Category := FullTimer;
Salary := 1000;
Bonus := 100;
// writing fields' values
writeln('Name : ',Name);
writeln('Salary : ',Salary:10:2);
writeln('Bonus : ',Bonus:10:2);
// assigning fields' values
Name := 'Albert Einstein';
Category := PartTimer;
Payment := 500;
// writing fields' values
writeln('Name : ',Name);
writeln('Payment : ',Payment:10:2);
end;
readln;
end.

You can download the complete code here.

Accessing Record’s Elements

2010-06-11T17:15:00.000-07:00

After we declare a record ( previous tutorial ), now we are going to access the elements or fields of the record. The fields in a record can be accessed using this notation :

RecordName.RecordField

Between the field name and the record name separated by a dot.

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

type
TRecordItem = record
Item : string;
Quantity : integer;
Price : currency;
end;
var
ItemStock : TRecordItem;

begin
// assigning values to record's fields
ItemStock.Item := 'USB Flash Disk';
ItemStock.Quantity := 20;
ItemStock.Price := 10;
// writing teh fields' values.
writeln('Item : ',ItemStock.Item);
writeln('Quantity : ',ItemStock.Quantity,' pc/s');
writeln('Price : $ ',ItemStock.Price:10:2 );
readln;
end.

Using with statement

With statement allows us to access a record field without mentioning the record name. The syntax of with statement is :

with Record do
begin
statements
end;

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

type
TRecordItem = record
Item : string;
Quantity : integer;
Price : currency;
end;
var
ItemStock : TRecordItem;

begin
with ItemStock do
begin
// assigning values to record's fields
Item := 'USB Flash Disk';
Quantity := 20;
Price := 10;
// writing teh fields' values.
writeln('Item : ',Item);
writeln('Quantity : ',Quantity,' pc/s');
writeln('Price : $ ',Price:10:2 );
end;
readln;
end.

You can download the complete code here.

Record

2010-06-09T17:30:00.000-07:00

Record is a structured data type. It contains some elements or fields, and each field can have a different data type. See the picture below.

How to declare a record ?

You have to declare a record after type clause.

type

RecordTypeName = record

Field_1 : DataType;

Field_n : DataType;

End;

var

RecordName : RecordTypeName;

For example, we declare a record named ItemStock that has three fields ( Item, Quantity and Price ).

type

TRecordItem = record

Item : string;

Quantity : integer;

Price : currency;

end;

var

ItemStock : TRecordItem;

First, define a TRecordItem then use it to declare a variable named ItemStock. So the ItemStock variable has three fields : Item, Quantity and Price.

Memory Game

2010-05-31T17:58:00.000-07:00

In this project, we are going to create a memory game. I think there are three steps of creating a memory game.

Step 1 : Create the form / user interface

Step 2 : Set the properties of the components

Step 3 : Write the code

Step 1 : Create the form / user interface

First you have to create a form with some image components, a label, a start button, a timer and an exit button. You can set any width or height properties of your components you use. And arrange them like the picture below or you can use your own arrangement.

Then cover all images with buttons. So your form will be like this :

Step 2 : Set the properties of the components

Now, set the properties of all components we use in this project like tables below :

Form

Property	Value
Caption	MEMORY GAME
Position	poDesktopCenter

Buttons

Component	Property	Value
StartButton	Name	StartButton
StartButton	Caption	&Start
ExitButton	Name	ExitButton
ExitButton	Caption	&Exit
Button1 .. Button20	Caption	?

Label

Property	Value
Caption	MEMORY GAME

Images

Property	Value
Stretch	true

Timer

Property	Value
Interval	1000
Enabled	false

Step 3 : Write the code

Before we start writing the code, we need to prepare some pictures for this project. I have prepared 30 pictures that you can download (jpg format). Or you can have your own pictures. If your pictures are in jpg format, you have to declare it in the uses clause.

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls, jpeg;

To see the complete code, you can download this project here.

Example program of using BinaryToInteger.DLL

2010-05-28T18:47:00.000-07:00

In this example, we are going to create a program that can convert an eight binary data into an integer value using BinaryToInteger.DLL. Before we start, you have to create a user interface like this picture.

Every edit box holds a bit of binary data. So there is a byte binary data (8 bits) that will be converted into an integer value. A binary data holds ‘0’ or ‘1’, so we need to limit the input of each edit box. And the code will be :

procedure TForm1.bit8KeyPress(Sender: TObject; var Key: Char);
begin
if not (key in ['0','1',#8,#13]) then
key:=#0
else
bit7.SetFocus;
end;

To use BinaryToInteger.DLL, you must declare the function after {$R *.DFM}

{$R *.DFM}
function BinToInt(S : String): integer; stdcall; external 'BinaryToInteger.dll';

Don forget, you must place your BinaryToInteger.DLL in the same folder with this project, or you can place this DLL file in the directory : c:\windows\system.

The code of OnClick even of ConvertButton :

procedure TForm1.ConvertButtonClick(Sender: TObject);
var
BinaryData : string;
begin
BinaryData := bit8.Text + bit7.Text + bit6.Text + bit5.Text +
b it4.Text + bit3.Text + bit2.Text + bit1.Text;
IntegerValue.Caption := IntToStr(BinToInt(BinaryData));
end;

You can download the complete code of this example program here.

BinaryToInteger.DLL

2010-05-28T18:36:00.000-07:00

Now, we're going to create a DLL file named BinaryToInteger.DLL This DLL is for converting “a character string of binary” into an integer value.

Example :

‘11111110’ = 254

The complete code of BinaryToInteger.DLL (click to download)

library BinaryToInteger;

uses
SysUtils,
Classes;

{$R *.RES}

function BinToInt(S : string) : integer; stdcall;
var
DataLength, i, j, buffer, buffer1 : integer;
begin
DataLength := Length(S);
buffer1 := 0;
for i := 1 to DataLength do
begin
buffer := StrToInt(S[i]);
for j := 1 to DataLength-i do buffer := buffer*2;
buffer1 := buffer1 + buffer;
end;
BinToInt := buffer1;
end;

exports
BinToInt;

begin
end.

To use this DLL file, you can see the example of using BinaryToInteger.DLL

Dynamic Array

2010-05-26T22:50:00.000-07:00

Dynamic array is an array that has no fix amount. To declare a dynamic array you can use this syntax :

Array of datatype;

Example :

Var

MyArray : array of integer;

This array is dynamic with integer data type. The memory of array is not allocated. To allocate memory of array use SetLength procedure.

Example :

SetLength(MyArray, 5);

SetLength(MyArray, 2, 3);

SetLength(MyArray, 2, 3, 5);

It will allocate an array which has five elements. In this case the index will be 0, 1, 2, 3, 4. And to free the array memory, set nil value to the array.

Example :

MyArray := nil;

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
i, sum : integer;
MyArray : array of integer;
begin
SetLength(MyArray, 5);
MyArray[0] := 12;
MyArray[1] := 14;
MyArray[2] := 16;
MyArray[3] := 18;
MyArray[4] := 20;
sum := 0;
for i:= 0 to Length(MyArray) -1 do
begin
sum := sum + MyArray[i];
end;
writeln(sum);
readln;
end.

You can download the complete code here.

3-Dimensional Array

2010-05-25T17:30:00.000-07:00

3-dimensional array is an array that has three indexes. To understand the concept of 3-dimensional array, see the picture below.

To declare 3-dimensional array that can hold 24 character, we can us this statement :

Type

TwoDimensionalArray = array[1..2, 1..3, 1..4] of char;

Var

TheData : TwoDimensionalArray;

Or you can use this statement :

Var

TheData : array[1..2, 1..3, 1..4] of char;

To access an element in 3-dimensional array use this syntax :

ArrayVariableName[ArrayIndex1, ArrayIndex2, ArrayIndex3];

Example :

TheData[1,3,4] := ‘A’;

Writeln(TheData[1,3,4]);

Readln(TheData[1,3,4]);

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
i, j, k : integer;
Thedata : array[1..2, 1..3, 1..2] of char;
begin
TheData[1,1,1] := 'A';
TheData[1,1,2] := 'B';
TheData[1,2,1] := 'C';
TheData[1,2,2] := 'D';
TheData[1,3,1] := 'E';
TheData[1,3,2] := 'F';
TheData[2,1,1] := 'G';
TheData[2,1,2] := 'H';
TheData[2,2,1] := 'I';
TheData[2,2,2] := 'J';
TheData[2,3,1] := 'K';
TheData[2,3,2] := 'L';
for i := 1 to 2 do
begin
for j := 1 to 3 do
begin
for k := 1 to 2 do writeln(TheData[i,j,k]);
end;
end;
readln;
end.

You can download the complete code here.

N-Dimensional Array

2010-05-24T19:10:00.000-07:00

N-dimensional array is an array that has two or more indexes. To understand the concept of n-dimensional array, see the picture below.

To declare two-dimensional array that can hold six character, we can us this statement :

Type

TwoDimensionalArray = array[1..2, 1..3] of char;

Var

TheData : TwoDimensionalArray;

Or you can use this statement :

Var

TheData : array[1..2, 1..3] of char;

To access an element in two-dimensional array use this syntax :

ArrayVariableName[ArrayIndex1,ArrayIndex2];

Example :

TheData[1,3] := ‘A’;

Writeln(TheData[1,3]);

Readln(TheData[1,3]);

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;
var
i, j : integer;
TheData : array[1..2, 1..3] of char;
begin
//assigning values to array
TheData[1,1] := 'A';
TheData[1,2] := 'B';
TheData[1,3] := 'C';
TheData[2,1] := 'D';
TheData[2,2] := 'E';
TheData[2,3] := 'F';
for i := 1 to 2 do
begin
for j := 1 to 3 do writeln(TheData[i,j]);
end;
readln;
end.

You can download the complete code here.

How to declare a three-dimensional array and to use it in a program ?

Array Data Type

2010-05-23T17:49:00.000-07:00

Array is a structured data type that can hold some data which has same data type. Every element in an array has an index and it can be individually accessed. In Pascal, we can have one-dimensional array or n-dimensional array.

To declare one-dimensional array that can hold six character, we can us this statement :

Type

OneDimensionalArray = array[1..6] of char;

Var

TheData : OneDimensionalArray;

Or you can use this statement :

Var

TheData : array[1..6] of char;

The statement above declares an array that can hold six elements. It is called static array, because it has a fix amount of data. While a dynamic array does not have a fix amount of data.

To access an element in an array use this syntax :

ArrayVariableName[ArrayIndex];

Example :

TheData[3] := ‘A’;

Writeln(TheData[3]);

Readln(TheData[3]);

Example program :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;
var
i : integer;
TheData : array[1..5] of char;
begin
//assigning values to array
TheData[1] := 'A';
TheData[2] := 'B';
TheData[3] := 'C';
TheData[4] := 'D';
TheData[5] := 'E';
for i := 1 to 5 do writeln(TheData[i]);
readln;
end.

You can download the complete code here.

Creating Web Photo Gallery using Photoshop

2010-05-20T19:52:00.000-07:00

It is quite simple to create a web photo gallery. Before we start creating a web photo gallery, first you have to group all picture you are going to use in your photo gallery into a folder / directory. Then you also need to prepare a folder / directory as a destination of your photo gallery.

After you run Adobe Photoshop, choose File – Automate – Web Photo Gallery. See the picture below :

A dialog box will appear. Choose the style of your photo gallery ( in this case I use simple style ) and the extension of your index file ( htm or html ). Define the directories or folders of your source images / pictures and the destination folder. In this case, I group all images / pictures in folder : D:\Fujiyama and the destination folder is D:\MyWebPhotoGallery. See the picture below :

Press OK and relax while Adobe Photoshop is processing your images / pictures. After processing, you will get some folders and files as the result in the destination folder.

Now, you ready to upload all the files to your web server.

Download pictures and web photo gallery here

Break and Continue Statement ( Delphi Tutorial # 14 )

2010-05-19T17:35:00.000-07:00

Break

Break is a procedure to jump out or quit the looping statement (if, repeat or while). Break is usually called in an if statement.

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number, stop : integer;
begin
write('Conter will be stopped at : ');
readln(stop);
for number := 1 to 1000 do
begin
if number = stop +1 then break;
writeln(number);
end;
readln;
end.

Continue

Continue is a procedure that is used for skipping to next iteration in a looping statement (if, repeat or while). It is also called in an if statement.

Example 1 (writing odd numbers from 1 to 20) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number : integer;
begin
for number := 1 to 20 do
begin
if Odd(number) then continue;
writeln(number);
end;
readln;
end.

Example 2 (writing even numbers from 1 to 20) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number : integer;
begin
for number := 1 to 20 do
begin
if not Odd(number) then continue;
writeln(number);
end;
readln;
end.

You can download the complete code here.

Go to Previous Tutorial or Next Tutorial

While Statement in Delphi ( Delphi Tutorial # 13 )

2010-05-18T19:51:00.000-07:00

The syntax of while statement is :

while boolean expression do

begin

first statement

last statement

end;

If the boolean expression is true, the statements will be executed until the boolean expression is false.

Example 1 ( writing numbers from 1 to 10 ) :

program Project1;

{$APPTYPE CONSOLE}

uses

SysUtils;

var

number : integer;

begin

number := 1;

while number < 11 do

begin

writeln(number);

number := number + 1;

end;

readln;

end.

Example 2 ( adding numbers from 1 to 100 ) :

program Project1;

{$APPTYPE CONSOLE}

uses

SysUtils;

var

number, sum : integer;

begin

number := 1;

sum := 0;

while number < 101

begin

sum := sum + number;

number := number + 1;

end;

writeln(sum);

readln;

end.

Example 3 ( adding odd numbers from 1 to 10 ) :program Project1;

program Project1;

{$APPTYPE CONSOLE}

uses

SysUtils;

var

number, sum : integer;

begin

number := 1;

sum := 0;

while number < 101

begin

if Odd(number) then sum := sum + number;

number := number + 1;

end;

writeln(sum);

readln;

end.

Example 4 ( adding even numbers from 1 to 100 ) :

program Project1;

{$APPTYPE CONSOLE}

uses

SysUtils;

var

number, sum : integer;

begin

number := 1;

sum := 0;

while number < 101

begin

if not Odd(number) then sum := sum + number;

number := number + 1;

end;

writeln(sum);

readln;

end.

You can download the complete code here.

Go to Previous Tutorial or Next Tutorial

Repeat Statement in Delphi ( Delphi Tutorial # 12 )

2010-05-16T21:21:00.000-07:00

The syntax of repeat statement is :

repeat

first statement

last statement

until boolean expression

The first statement until the last statement will be executed once. If the boolean expression is false, all statements will be executed again until the boolean expression is true.

Example 1 ( writing numbers from 1 to 10 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number : integer;
begin
number := 1;
repeat
writeln(number);
number := number + 1;
until number = 11;
readln;
end.

Example 2 ( adding numbers from 1 to 100 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number, sum : integer;
begin
number := 1;
sum := 0;
repeat
sum := sum + number;
number := number + 1;
until number = 101;
writeln(sum);
readln;
end.

Example 3 ( adding odd numbers from 1 to 10 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number, sum : integer;
begin
number := 1;
sum := 0;
repeat
if Odd(number) then sum := sum + number;
number := number + 1;
until number = 101;
writeln(sum);
readln;
end.

Example 4 ( adding even numbers from 1 to 100 ) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number, sum : integer;
begin
number := 1;
sum := 0;
repeat
if not Odd(number) then sum := sum + number;
number := number + 1;
until number = 101;
writeln(sum);
readln;
end.

You can download the complete code here.

Go to Previous Tutorial or Next Tutorial

Looping Statement in Delphi ( Delphi Tutorial # 11 )

2010-05-16T20:51:00.000-07:00

Looping statement is used for repeating a process. For example, if we want to write numbers from 1 to 100, we can use looping statement instead of writing a hundreds statements. In Pascal, there are three looping statements :

- for statement

- repeat statement

- while statement

We have break statement and continue statement related to repetition process.

For statement

The syntax of for statement :

- for counter := first value to last value do

- for counter := first value downto last value do

Counter is an ordinal type variable (see Delphi Tutorial # 3 : Identifier and Data Type). First value and last value are expressions which data type is the same as counter’s data type. Counter’s value will change from the first value to the last value. And in every step of counter, the statement will be executed.

Example 1 :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
number : integer;
letter : char;
begin
for number:=1 to 5 do
writeln(number);
for letter:='A' to 'E' do
writeln(letter);
for number:=5 downto 1 do
writeln(number);
for letter:='E' downto 'A' do
writeln(letter);
readln;
end.

Example 2 (adding numbers between 1 to 100) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
i, sum : integer;
begin
sum := 0;
for i:=1 to 100 do
begin
sum := sum + i;
end;
writeln(sum);
readln;
end.

Example 3 (adding odd numbers between 1 to 100) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
i, sum : integer;
begin
sum := 0;
for i:=1 to 100 do
begin
if Odd(i) then
sum := sum + i;
end;
writeln(sum);
readln;
end.

Example 4 (adding even numbers between 1 to 100) :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
i, sum : integer;
begin
sum := 0;
for i:=1 to 100 do
begin
if not Odd(i) then
sum := sum + i;
end;
writeln(sum);
readln;
end.

You can download the complete code here

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Multiple Conditional Statements in Delphi ( Delphi Tutorial # 10 )

2010-05-16T19:15:00.000-07:00

You can use if statement for multiple conditional statement but it will be little bit messy.

For example :

program multiple_cond_if;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
mark : integer;
begin
write('Your mark : ');
readln(mark);
write('Your grade is ');
if mark >= 90 then
writeln('A')
else
if mark >= 70 then
writeln('B')
else
if mark >= 60 then
writeln('C')
else
if mark >= 40 then
writeln('D')
else
writeln('E');
readln;
end.

Instead of using if … then statement, it will be easier using case … of statement :

program multiple_cond_case;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
mark : integer;
begin
write('Your mark : ');
readln(mark);
write('Your grade is ');
case mark of
0..39 : writeln('E');
40..59 : writeln('D');
60..69 : writeln('C');
70..89 : writeln('B');
90..100 : writeln('A');
end;
readln;
end.

Download the complete code here.

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Using DLL file in Delphi

2010-05-13T18:57:00.000-07:00

After we created a DLL file in the previous tutorial, now we’re going to use this DLL file in an application. First, you have to create a user interface like picture below :

Or you can download this project here.

Before you write some codes in this project, you have to make sure that the DLL file you’re going to use and your project are in the same directory (folder). Or you can put the DLL file you’re going to use in directory : c:\windows\system.

To use functions in a DLL file we’ve created, you must type the function after {$R *.DFM}

{$R *.DFM}
{ place functions from DLL here }
function area(length, width : integer): integer; stdcall; external 'area_volume.dll';
function volume(length, width, height : integer): integer; stdcall; external 'area_volume.dll';

external clause means that the functions we use (area and volume) are in an external file (area_volume.dll)

To call area function and volume function see the codes below :

procedure TForm1.CalculateAreaButtonClick(Sender: TObject);
var
L, W : integer;
begin
L := StrToInt(Edit1.Text);
W := StrToInt(Edit2.Text);
Label8.Caption := Label8.Caption + ' ' + IntToStr(area(L,W));
end;

procedure TForm1.CalculateVolumeButtonClick(Sender: TObject);
var
L, W, H : integer;
begin
L := StrToInt(Edit3.Text);
W := StrToInt(Edit4.Text);
H := StrToInt(Edit5.Text);
Label9.Caption := Label9.Caption + ' ' + IntToStr(volume(L,W,H));
end;

area(L,W) and volume(L,W,H) will return integer type values, so if you want to put these values into label.caption, you have to convert them into string using IntToStr() procedure.

You can download the complete code here.

if Statement in Delphi ( Delphi Tutorial # 9 )

2010-05-13T18:13:00.000-07:00

There are two kinds of conditional statement : if statement and case statement. This both statements are for making decisions that involve two or more alternative choices or conditions.

In this tutorial, we will learn about if statement. There are two kinds of if statement :

- if ….. then

- if ….. then …. else

The syntax of if …. then statement is :

If boolean expression then statement;

Boolean expression can be true or false. If it is true, computer will execute the statement. If it is false, computer will not execute the statement.

The syntax of if …. then …. else statement is :

If boolean expression then first_statement else second_statement;

If boolean expression is true, computer will execute the first statement. If it is false, computer will execute the second statement.

The flowchart of if statement is below :

Example for if …. then statement :

program Project1;

{$APPTYPE CONSOLE}

uses SysUtils;

var

score : integer;

begin

write('Your score : ');

readln(score);

if score < 60 then writeln('You did not pass the exam');

if score >= 60 then writeln('You passed the exam');

readln;

end.

Example for if …. then …. else statement :

program Project2;

{$APPTYPE CONSOLE}

uses

SysUtils;

var

score : integer;

begin

write('Your score : ');

readln(score);

if score < 60 then

writeln('You did not pass the exam')

else

writeln('You passed the exam');

readln;

end.

Both projects above will give you the same result.

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Creating DLL file using Delphi

2010-05-11T20:00:00.000-07:00

There are two kinds of executable file in Windows, EXE file and DLL file. DLL (Dynamic Link Library) is an executable file with some procedures or functions in it. These procedures or functions can be used by some applications at the same time. Because, once DLL is loaded to memory, every program or application can use it. The other advantage of using DLL is our application becomes modular. It will be easier to change the application by replacing the DLL.

To create a DLL file, choose File – New – DLL. And you’ll get some codes below :

library Project1;

{ Important note about DLL memory management: ShareMem must be the first unit in your library's USES clause AND your project's (select Project-View Source) USES clause if your DLL exports any procedures or functions that pass strings as parameters or function results. This applies to all strings passed to and from your DLL--even those that are nested in records and classes. ShareMem is the interface unit to the BORLNDMM.DLL shared memory manager, which must be deployed along with your DLL. To avoid using BORLNDMM.DLL, pass string information using PChar or ShortString parameters. }

uses

SysUtils,

Classes;

{$R *.RES}

begin

end.

You can delete the unnecessary comment after library clause and add exports clause before begin….end block.

One thing you have to concern about is that all variables in DLL are private. Your application and DLL can not use the variables at the same time. You have to send values of the variables and receive a result.

Now we’re going to insert some functions into DLL :

library area_volume;

uses

SysUtils,

Classes;

{$R *.RES}

function area(length, width : integer): integer; stdcall;

begin

area := length*width;

end;

function volume(length, width, height : integer): integer; stdcall;

begin

volume := length*width*height;

end;

exports

area, volume;

begin

end.

You can download this source code here.

Now save the project as area_volume.dpr. Remember that the project name and the DLL name have to be the same, in this case we name it area_volume. Then build the DLL file by choosing Project – Build … And you’ll get area_volume.dll file. Then you can create an application using this DLL.

Square Root and Exponential Function in Delphi ( Delphi Tutorial # 8 )

2010-05-10T18:10:00.000-07:00

Sqrt() function

In this tutorial we’re going to write some mathematic formulas in Delphi. The first formula is :

To write the above formula in Delphi, we use sqrt() function :

Sqrt((b*b-4*a*c)/(2*a))

Exp() function

There’s no power operator in Pascal Object. But it does not mean that we can not calculate the formula above. Before we calculate the formula, we have to describe it into an exponential function :

So we can write the formula using exp() function and ln() function :

Exp(b*ln(a))

Example :

program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;

var
x, y : real;
a, b, c : integer;

begin
// Insert user code here
a := 2;
b := 5;
c := 3;
x := sqrt((b*b-4*a*c)/(2*a));
writeln(x:0:1);
y := exp(b*ln(a));
writeln(y:0:0);
readln;
end.

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Text Area Code Generator

2010-05-05T22:07:00.000-07:00

In this first project, we're going to create an application that can generate HTML codes to create a text area. First you have to create a form like the picture below :

Now, write the codes for each event of the components :

When the first time we run the program, we set the default values of some component's properties. So we write some codes on FormActivate event of Form1 :

procedure TForm1.FormActivate(Sender: TObject);
begin
Memo1.Text := '';
Memo2.Text := '';
Memo2.SetFocus;
Edit1.Enabled := false;
Edit2.Enabled := false;
Edit3.Enabled := false;
RadioButton1.Checked := true;
RadioButton2.Checked := false;
RadioGroup1.ItemIndex := 0;
Edit4.Text := '1';
Edit5.Text := '1';
end;

The codes for RadioButtons ( Text Only and Link Codes ) :

procedure TForm1.RadioButton1Click(Sender: TObject);
begin
Edit1.Enabled := false;
Edit2.Enabled := false;
Edit3.Enabled := false;
Memo2.Enabled := true;
Memo2.SetFocus;
end;

procedure TForm1.RadioButton2Click(Sender: TObject);
begin
Edit1.Enabled := true;
Edit2.Enabled := true;
Edit3.Enabled := true;
Memo2.Enabled := false;
Edit1.SetFocus;
end;

We need to limit the input of rows and columns for numeric inputs only :

procedure TForm1.Edit4KeyPress(Sender: TObject; var Key: Char);
begin
if not (key in ['0'..'9', #8]) then key := #0;
end;

procedure TForm1.Edit5KeyPress(Sender: TObject; var Key: Char);
begin
if not (key in ['0'..'9', #8]) then key := #0;
end;

And the other codes for the events of the rest components are :

procedure TForm1.GenerateButtonClick(Sender: TObject);

var

LinkBanner : string;

begin

if RadioButton1.Checked then

begin

memo1.Text :='<p align="'+RadioGroup1.Items.String

[RadioGroup1.ItemIndex]+'"><textarea name="code" rows="' +

Edit4.Text + '" cols="' +Edit5.Text + '">' + memo2.Text +

'</textarea></p>';

end else

begin

LinkBanner := '<a href="' + Edit2.Text +

'"target="_blank"><img src="'+Edit1.Text +

'" border="0" alt="' + Edit3.Text + '" /></a>';

memo1.Text := RadioGroup1.Items.Strings[RadioGroup1.ItemIndex] +

'"><textarea name="code" rows="' +

Edit4.Text + '" cols="'+Edit5.Text + '">' + LinkBanner +

'</textarea></p>';

end;

procedure TForm1.ClearButtonClick(Sender: TObject);

begin
memo1.Text := '';

end;

procedure TForm1.ExitButtonClick(Sender: TObject);
begin
Application.Terminate;
end;

To see the complete codes you can download this project here.

Creating Text Area

2010-05-05T21:54:00.000-07:00

What is text area ? You can see the example of text area below :

Your Text Here

To create a text area, use this HTML tag :

You can save some HTML codes that contain a link and a banner for link or banner exchange. So the codes can be copied and pasted into another web page. To create a text area with a link and a banner, use these HTML codes :

Text Area Code Generator

You can also use Text Area Code Generator to create a text area.

Using this software, you don’t need to type the HTML code to create a text area. You can generate the code by clicking Generate HTML Codes button. Click here to download this software.

Operators ( Example Console Program using Delphi )

2010-04-28T22:54:00.000-07:00

This is an example program using operators

program Using_Operators;

{$APPTYPE CONSOLE}
uses
SysUtils;

begin
// Insert user code here
writeln('7 + 8 = ', 7 + 8);
writeln('7 - 8 = ', 7 - 8);
writeln('7 x 8 = ', 7 * 8);
writeln('15 : 3 = ', 15/3:0:0);
{ :0:0 is for formatting. You should try to ommit it }
{ and see what happend at the result }
writeln('17 mod 4 = ', 17 mod 4);
writeln('17 div 4 = ', 17 div 4);
writeln('3 + 2 x 4 = ', 3 + 2 * 4); // see the different between
writeln('(3 + 2) x 4 = ', (3 + 2) * 4); // these two expressions
writeln(8 shr 1); // logic operator
writeln(8 shl 1); // logic operator
writeln(1 = 2); // boolean operator
writeln(not (1 = 2)); // boolean operator
writeln(7 >= 2); // relational operator
writeln('a' < 'b'); // relational operator
writeln('123delphicodes' = '123delphicodes'); // string operator
writeln('123DelphiCodes' = '123delphicodes'); // string operator
writeln('123DelphiCodes' < '123delphicodes'); // string operator
readln; // wait until enter button is pushed
end.

Delphi Tutorial # 7

2010-04-28T20:44:00.000-07:00

Operators

Operator is a symbol to do some operation, such as : sum, product, division, compare etc. Operator involves two or more operands. Operator and operand form an expression. Example :

12 + 15 = 27

see the table below :

Operators	Operands
+	12
=	15
	27

arithmetic operators

Operator
*
/
div
mod
+
-

logic operators

Operator
not
and
or
xor
shl
shr

boolean operators

Operator
not
and
or
xor

relational operators

Operator
>
<
>=
<=
<>
=

string operator

all relational operators also can be use for string :

Operator
>
<
>=
<=
<>
=

In the example, I will show you how to use these operators.

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Delphi Tutorial # 6

2010-04-23T18:30:00.000-07:00

Console Application

Before we go further with visual programming, it is important to understand the basic element of Delphi. In the first tutorial about, I have mention that a console application is a DOS (Disk Operating System) application. It is a non Windows application. Using console programming, you can focus on the codes only. Meanwhile you can forget about visual programming, and learn about Pascal language.

To make a console application, choose File – Close All (if thee is still a form in IDE). Then choose File – New, select Console Application. Delphi will show Project1.dpr window :

Declare constants and variables after uses SysUtils;

const

length : integer = 12;

width : integer = 8;

var

area : integer;

Insert user code between begin …. end.

area := length*width;

writeln('Length of rectangle = ',length);

writeln('Width of rectangle = ',width);

writeln('The area = ',area);

readln;

The complete codes of Project1.dpr :

program Project1;

{$APPTYPE CONSOLE}

uses

SysUtils;

const

length : integer = 12;

width : integer = 8;

var

area : integer;

begin

// Insert user code here

area := length*width;

writeln('Length of rectangle = ',length);

writeln('Width of rectangle = ',width);

writeln('The area = ',area);

readln;

end.

Run the program, and the result is :

The last code readln; is for delaying program until you press Enter button.

Comment

// Insert user code here is an example of comment. Comment can be written in three ways :

- Written between { }

- Written between * *

- Begun with // like the example above

Assigning a value to a variable

From the program above, we assign a value to area variable using assignment operator :=. The syntax is :

variable := value;

so the code is :

area := length*width;

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Showing the Hidden Files in Windows XP

2010-04-22T18:09:00.000-07:00

Windows hides the important system files. But Some of hidden files are dangerous to our system. And we can call them viruses. Here is the way to make all hidden files shown : Run windows explorer by clicking the mouse right button on Start Menu. Then choose Explore.

Choose Tools – Folder Option, like the picture above. The Folder Option window will appear :

Choose Show hidden files and folders. Remove the checklist form Hide extensions for known file type and Hide protected operating system files (Recommended). Click Apply, then OK. Now all hidden files will be shown.

Enabling Turn Off Autoplay

2010-04-21T22:03:00.000-07:00

Windows provides Autoplay feature to examine a removable media that newly discovered by the system. It is closely like AutoRun feature. Removable media can be a flashdisk, a CD, a DVD, a memory card or an external hard disk etc.

But this feature has a disadvantage. If the removable media connected to the computer is infected by some viruses, the virus will be automatically loaded to memory, or even your system will be automatically infected. Virus is usually an executable hidden file. And in a certain way will be automatically executed when a media or a directory / folder is being connected to the system. Usually by using an autorun.inf file.

To avoid this, we have to enable Turn Off Autoplay feature. From Start Up menu, choose Run. Type gpedit.msc then click OK.

The Group Policy window will appear :

There are two configuration : Computer Configuration and User Configuration. Form Computer Configuration, choose Administrative Templates - System, then choose Turn off Autoplay as the picture shown below :

Then Turn off Autoplay Properties window will appear. Choose Enabled and All drives. Then click Apply – OK :

You also have to do these steps for User Configuration. Choose Administrative Templates - System, then choose Turn off Autoplay as the picture shown below :

Choose Enabled and All drives. Then click Apply – OK.

Once the Turn Off Autoplay feature has been enabled, just remember do not ever double click a folder or a media that is infected by viruses. It is more save to use Windows Explorer, by clicking the mouse right button on Start Menu, then choose Explorer. In this way, the hidden viruses will not be executed. It will decrease the risk of viral infection to your system. Then all you have to do is deleting suspicious hidden files. But before you can do this, you have to make all the hidden files shown.

Delphi Tutorial # 5

2010-04-14T18:24:00.000-07:00

Program Structure

A program is composed of three elements :

- Program Title

- Uses Clauses

- Declarations and Statements

Program title is the name of the program. Uses clauses include units that are used in the program. Declarations and statements are codes that will be executed by computer.

You can see an example of Delphi program structure in Delphi Tutorial # 2. See the codes project1.dpr file below :

program Project1;

uses

Forms,

Unit1 in 'Unit1.pas' {MyForm};

{$R *.RES}

begin

Application.Initialize;

Application.CreateForm(TMyForm, MyForm);

Application.Run;

end.

The example above does not have declarations. Declaration is where we define constants, types, variables, procedures and functions. The structure of declarations is shown below :

Const

{constants list}

Type

{types create by user}

Var

{variables list}

{functions and procedures}

Function is a routine that can be called by the program and will return a value. Procedure is a routine that does not return a value.

A program is usually formed by some source code modules that called units. A unit consist some routine (functions and procedures). It is saved as a unit file (.PAS). The structure of a unit is shown below :

Unit unitname;

Interface

Uses {units}

{interface}

Implementation

Uses {units}

{implementation}

Initialization

{Initialization}

Finalization

{Finalization}

End.

The example of a unit is unit1.pas file :

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls;

type

TMyForm = class(TForm)

Label1: TLabel;

ExitButton: TButton;

procedure ExitButtonClick(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

MyForm: TMyForm;

implementation

{$R *.DFM}

procedure TMyForm.ExitButtonClick(Sender: TObject);

begin

Application.Terminate;

end;

end.

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Click and Drag Mouse to Draw a Line Using Delphi

2010-04-12T17:58:00.000-07:00

To draw a line with click and drag method, we use some events related with mouse : OnMouseDown, OnMouseMove and OnMouseUp. OnMouseDown is an event when we push the left mouse button. OnMouseMove is when we move the cursor. And OnMouseUp is when we release the mouse button. First, prepare a user interface ( a blank form and a button) :

Now, you have to decide what action should be done on each event ( OnMouseDown, OnMouseMove and OnMouseUp ) :

Event	Action
OnMouseDown	get the x and y start point
OnMouseMove	- delete the old line
OnMouseMove	- draw the new line
OnMouseUp	- draw the line
OnMouseUp	- finish drawing

The complete source code is listed below :

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

StdCtrls;

type

TForm1 = class(TForm)

Button1: TButton;

procedure FormMouseDown(Sender: TObject; Button: TMouseButton;

Shift: TShiftState; X, Y: Integer);

procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,

Y: Integer);

procedure FormMouseUp(Sender: TObject; Button: TMouseButton;

Shift: TShiftState; X, Y: Integer);

procedure Button1Click(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

Drawing : boolean;

StartX, StartY, EndX, EndY : integer;

implementation

{$R *.DFM}

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

Shift: TShiftState; X, Y: Integer);

begin

Drawing := true;

StartX := x;

StartY := y;

EndX := x;

EndY := y;

end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

Y: Integer);

begin

if Drawing then

begin

Canvas.Pen.Mode := pmNotXor;

Canvas.MoveTo(StartX,StartY);

Canvas.LineTo(EndX,EndY);

Canvas.MoveTo(StartX,StartY);

Canvas.LineTo(x,y);

end;

EndX := x;

EndY := y;

Canvas.Pen.Mode := pmCopy;

end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;

Shift: TShiftState; X, Y: Integer);

begin

Canvas.MoveTo(StartX,StartY);

Canvas.LineTo(x,y);

Drawing := false;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

Application.Terminate;

end;

end.

Run the program, and now you can click and drag your mouse to draw a line.

Delphi Tutorial # 4

2010-04-11T18:30:00.000-07:00

Identifier and Data Type

In this tutorial, we’re going to learn about Pascal Object - that serves as a basic for Delphi – such as data type, constant and variable. And you’ll be able to declare variables in a program and use operators in a statement.

Identifier

Identifier is used to declare constant, variable, unit, function, procedure etc. An identifier can be preceded by an underscore ( _ ), next character can be number, character string or underscore. The length of an identifier can be more than 255 characters, but only 255 first characters will be considered as an identifier. The rest characters will be ignored. Capital letter or small letter will be considered the same. And an identifier has to be non reserved word :

RESERVED WORD
and	array	as	asm
begin	case	class	const
constructor	destructor	dispinterface	div
do	downto	else	end
except	exports	file	finalization
finally	for	function	goto
if	implementation	in	inherited
initialization	inline	interface	is
label	library	mod	nil
not	object	of	or
out	packed	procedure	program
property	raise	record	repeat
resourcestring	set	shl	shr
string	then	threadvar	to
try	type	unit	until
used	var	while	with
xor	private	protected	public
published automated

Some examples of identifier are sum, salary, price, year etc. SALARY, Salary and salary are the same, because capital letter or small letter are considered the same.

Simple Data Type

Now we’ll learn some of data types in Pascal Object. Some of them categorize in simple data type. There are two simple data type : ordinal (integer, char, Boolean, string etc) and real.

Integer

Type	Range	Memory Size
Byte	0 to 255	1 byte
Word	0 to 65535	2 byte
ShortInt	-128 to 127	1 byte
SmallInt	-32768 to 32767	2 byte
Integer	-2147483648 to 2147483647	4 byte
Cardinal	0 to 2147483647	4 byte
LongInt	-2147483648 to 2147483647	4 byte

Char

Type	Memory Size	Saved Character
ANSIChar	1 byte	an ANSI Char
WideChar	2 byte	an Unicode Char
Char	1 byte	like an ANSIChar

Boolean

Type	Range	Memory Size
Boolean	one byte	1 byte
ByteBool	one byte	1 byte
Bool	one word	2 byte
WordBool	one word	2 byte
LongBool	double	4 byte

Real

String

Constant and Variable

Constant is a fixed value that is used in a program. To define a constant in a program, we use a reserved word const. Example :

const

discount = 0.1

const

discount : real = 0.1

discount is a constant which value is 0.1

But in a program, a value is not always fixed but it can be constantly changing. To handle this, we need variables. A variable can contain a value, and the value can be changed anytime. Before we can use a variable, it has to be declared first. Use reserved word var to declare a variable :

Var

Age : byte;

Address : string;

Salary : currency;

Age is a byte variable, its value can be 0 to 255. Address is a string variable. And Salary is a currency variable.

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Delphi Tutorial # 3

2010-04-09T21:04:00.000-07:00

Using Edit Box

In this tutorial, we’re going to learn using Edit component. Edit component or Edit box is in Standard page of component palette. An Edit box has some properties (such as Enabled, Name, Text, MaxLength, PasswordChar, ReadOnly, Visible etc.) and events (such as OnChange, OnEnter, OnExit, OnKeyPress, OnKeyUp etc.). Below is a table of some frequently used properties :

Using Edit Boxes for counting a rectangle area

For practicing using edit box, you need to create a form with some component like picture shown below :

First, change the form’s properties like table below :

Property	Value
Caption	Counting Rectangle Area
Name	FormRectangleArea
Position	poDesktopCenter

Add three labels into the form. And each label has properties like table below :

Label	Property	Value
Label1	Caption	Width
Label2	Caption	Length
Label3	Caption	Area

Then add three edit boxes into the form. Set the properties like table below :

Label	Property	Value
Label1	Caption	Width
Label2	Caption	Length
Label3	Caption	Area

The last component you need is a button, which has properties like table below :

Property	Value
Caption	&Count
Name	CountButton

Now, save the project into a folder with any name. Remember, that you have to save the project into a folder, because a Delphi project contains some files. Give meaningful names for the unit and the project you created, such as UnitRectangle and ProjectRectangle. Run the program by pressing F9. If you press the button, nothing happen because we haven’t written some codes yet.

Adding the codes

Countbutton is meant to count rectangle area by multiplying the value of width and length. To add codes, first click Countbutton. Activate the object inspector, click event tab, then double click the OnClick event. Type these codes :

procedure TFormRectangleArea.CountButtonClick(Sender: TObject);

var

W, L, A : integer;

begin

W := StrToInt(Width.Text);

L := StrToInt(Length.Text);

A := W * L;

Area.Text := IntToStr(A);

end;

Function StrToInt() is for converting a string value to integer, and function IntToStr() is for converting an integer value to string. An error will occur when you input a wrong width or length value. Ie : if you input 1A into width or length value, an error message will appear because 1A can not be converted into an integer value. To avoid this error, type these codes for OnKeyPress event of Width edit box and Length edit box :

procedure TFormRectangleArea.WidthKeyPress(Sender: TObject; var Key: Char);

begin

if not (key in ['0'..'9', #8]) then key := #0;

end;

procedure TFormRectangleArea.LengthKeyPress(Sender: TObject;

var Key: Char);

begin

if not (key in ['0'..'9', #8]) then key := #0;

end;

The code if not (key in ['0'..'9', #8] then key := #0 will set key value to #0 (null) if the value is not in 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or #8. #8 is Backspace.

Go to Previous Tutorial or Next Tutorial

Delphi Tutorial # 2

2010-04-09T20:48:00.000-07:00

Visual Programming Concept

In this tutorial, we’re going to learn about basic visual programming concept. We’re going to learn how to create a form including several components.

There are three steps of visual programming : Creating a user interface, Writing codes and Compiling code and form into an executable file (.EXE). When you run the program, Delphi will compile your codes into an EXE file automatically.

Creating a simple project

To create a project, first you must create a user interface. Resize the blank form into a desired size you like (you have to find out how to resize the form yourself). Set form properties like table shown below :

Caption	My First Delphi Project
Name	MyForm
Position	poDesktopCenter

Add a label component, it is in Standard page of component palette. Set label properties like table shown below :

Caption

This is my first Delphi project

Add a button component, it is also in Standard page of component palette. Set button properties like table shown below :

Caption	&Exit
Name	ExitButton

Now, we have a user interface below :

Adding codes for ExitButton

If you want to add some codes to ExitButton, you have to determine the event when the codes will be executed. Then you can write some codes for the event. In this case you have to write some codes for OnClick event of the ExitButton. From the event tab of object inspector, select or double click the OnClick event (see the picture).

Start writing the codes :

procedure TMyForm.ExitButtonClick(Sender: TObject)

begin

Application.Terminate;

end;

You only have to type a simple code : Application.Terminate; You have to put the(;) after the statement. This code will end your application.

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Export an Interbase Table into an MS Excel File

2010-04-07T18:14:00.000-07:00

After you create an MS Excel file ( previous tutorial 1 ) and set its attributes ( previous tutorial 2 ), now you can export your database to an MS Excel file. Add a table component into the form ( use the previous form you have created before ). Set the properties of the table :

Active	True
DatabaseName	ALIASMYDATA
Name	MyTable
TableName	EMPLOYEE

Now the form will be like the picture below :

To start exporting data from employee table to Excel, add some codes to our previous project in the previous tutorial. See the codes below, the new added codes are bold.

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

StdCtrls, ComObj, Db, DBTables;

type

TForm1 = class(TForm)

CreateExcel: TButton;

Exit: TButton;

MyTable: TTable;

procedure ExitClick(Sender: TObject);

procedure CreateExcelClick(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.CreateExcelClick(Sender: TObject);

var

ExcelApplication : variant;

Sheet : variant;

column, row : integer;

begin

try

begin

ExcelApplication := CreateOleObject('Excel.Application');

ExcelApplication.Visible := true;

end;

except

Showmessage('Cannot create an Excel file, make sure that MS Excel is installed on your system');

Application.Terminate;

end;

ExcelApplication.WorkBooks.Add(-4167);

ExcelApplication.WorkBooks[1].WorkSheets[1].Name := 'my data';

Sheet := ExcelApplication.WorkBooks[1].WorkSheets['my data'];

Sheet.Range['A1:D7'].Borders.LineStyle := 7;

Sheet.Range['A1:D7'].Borders.color := clblue;

Sheet.Columns[1].ColumnWidth := 4;

Sheet.Columns[2].ColumnWidth := 30;

Sheet.Columns[3].ColumnWidth := 8;

Sheet.Columns[4].ColumnWidth := 20;

Sheet.Cells[1,1] := 'ID';

Sheet.Cells[1,2] := 'NAME';

Sheet.Cells[1,3] := 'AGE';

Sheet.Cells[1,4] := 'PHONE NUMBER';

for row := 1 to MyTable.RecordCount do

begin

for column := 1 to MyTable.FieldCount do

begin

Sheet.Cells[row+1,column] := MyTable.Fields[column-1].AsString;

end;

MyTable.Next;

end;

end;

procedure TForm1.ExitClick(Sender: TObject);

begin

Application.Terminate;

end;

end.

Now you have an MS Excel File which consist data from employee table

Go to Previous Tutorial ( Setting Attributes of an Excel File )

Setting Attributes of an Excel File

2010-04-06T17:15:00.000-07:00

In the previous tutorial ( Creating an Excel File using Delphi ), you have learned how to create an MS Excel file. Now we need to set some attributes of the MS Excel file. In an MS Excel file, a cell has some attributes ie : font, color, border etc.

To set cell border, use this code :

ExcelApplication.WorkBooks[1].WorkSheets['my data']. Range['A1: D7'].Borders.LineStyle := 7;

Sheet.Range['A1: D7'].Borders.LineStyle := 7;

We can replace ExcelApplication.WorkBooks[1].WorkSheets['my data'] with Sheet because in the previous tutorial we have set our working worksheet into Sheet variable. The LineStyle value can be 0, 1, 2 ……13. You can try each value and see what happen to the worksheet.

To set cell border color :

Sheet.Range['A1:D7'].Borders.color := clblue;

To set cell font attributes :

Sheet.Range['A1: D7'].Font.color := clred;

Sheet.Range['A1: D7'].Font.Bold := true;

To set columns width :

Sheet.Columns[1].ColumnWidth := 4;

Sheet.Columns[2].ColumnWidth := 30;

Sheet.Columns[3].ColumnWidth := 8;

Sheet.Columns[4].ColumnWidth := 20;

To set rows height :

Sheet.Rows[1].RowHeight := 25;

Sheet.Rows[2].RowHeight:= 40;

Entering a value to a cell

In MS Excel worksheet, every cell has a name like A1, B12, AA7, BC8 etc. But we can not access cells with these names. Imagine that a worksheet is a two dimension array of cells. A1 equals to Cells[1,1], B12 equals to Cells[12,2], AA7 equals to Cells[7,27] etc. To enter a value to A1, B1, C1 and D1 cells, use these codes :

Sheet.Cells[1,1] := 'ID';

Sheet.Cells[1,2] := 'NAME';

Sheet.Cells[1,3] := 'AGE';

Sheet.Cells[1,4] := 'PHONE NUMBER';

Now add some codes to our previous project in the previous tutorial. See the codes below, the new added codes are bold.

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

StdCtrls, ComObj;

type

TForm1 = class(TForm)

CreateExcel: TButton;

Exit: TButton;

procedure ExitClick(Sender: TObject);

procedure CreateExcelClick(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.CreateExcelClick(Sender: TObject);

var

ExcelApplication : variant;

Sheet : variant;

begin

try

begin

ExcelApplication := CreateOleObject('Excel.Application');

ExcelApplication.Visible := true;

end;

except

Showmessage('Cannot create an Excel file, make sure that MS Excel is installed on your system');

Application.Terminate;

end;

ExcelApplication.WorkBooks.Add(-4167);

ExcelApplication.WorkBooks[1].WorkSheets[1].Name := 'my data';

Sheet := ExcelApplication.WorkBooks[1].WorkSheets['my data'];

Sheet.Range['A1:D7'].Borders.LineStyle := 7;

Sheet.Range['A1:D7'].Borders.color := clblue;

Sheet.Columns[1].ColumnWidth := 4;

Sheet.Columns[2].ColumnWidth := 30;

Sheet.Columns[3].ColumnWidth := 8;

Sheet.Columns[4].ColumnWidth := 20;

Sheet.Cells[1,1] := 'ID';

Sheet.Cells[1,2] := 'NAME';

Sheet.Cells[1,3] := 'AGE';

Sheet.Cells[1,4] := 'PHONE NUMBER';

end;

procedure TForm1.ExitClick(Sender: TObject);

begin

Application.Terminate;

end;

end.

Go to Previous Tutorial ( Creating an Excel File using Delphi )

or Next Tutorial ( Export an Interbase Table into an MS Excel File )

Creating an Excel File using Delphi

2010-04-05T17:58:00.000-07:00

In my opinion, knowing how to create an Excel file using Delphi is very important. Especially when you work with a database, sometimes - not always - you need to make a report in an Excel file. To do this, you have to use Object Linking and Embedding (OLE) function. OLE function will link to or embed data from other applications (servers) in another application (the client). In this case, MS Excel is the server application and our Delphi project is the client application.

Before we go further, create a user interface like picture below :

The OLE function for creating an Excel application is :

function CreateOleObject(const ClassName: string)

This function is in ComObj unit. Add this unit into the uses declaration in the program. Then type the codes below :

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

StdCtrls, ComObj;

type

TForm1 = class(TForm)

CreateExcel: TButton;

Exit: TButton;

procedure ExitClick(Sender: TObject);

procedure CreateExcelClick(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.CreateExcelClick(Sender: TObject);

var

ExcelApplication : variant;

Sheet : variant;

begin

try

begin

ExcelApplication := CreateOleObject('Excel.Application');

ExcelApplication.Visible := true;

end;

except

Showmessage('Cannot create an Excel file, make sure that MS Excel is installed on your system');

Application.Terminate;

end;

ExcelApplication.WorkBooks.Add(-4167);

ExcelApplication.WorkBooks[1].WorkSheets[1].Name := 'my data';

Sheet := ExcelApplication.WorkBooks[1].WorkSheets['my data'];

end;

procedure TForm1.ExitClick(Sender: TObject);

begin

Application.Terminate;

end;

end.

The explanation :

Action	Codes
Declare two variables : ExcelApplication and Sheet as variant	ExcelApplication : variant; Sheet : variant;
Create an MS Excel application using try…except… clause and CreateOleObject function. Then make it visible	ExcelApplication := CreateOleObject('Excel.Application'); ExcelApplication.Visible := true;
Create a blank Excel workbook	ExcelApplication.WorkBooks.Add(-4167);
Create a blank Excel worksheet	ExcelApplication.WorkBooks[1].WorkSheets[1].Name := 'my data';
Set the working worksheet into Sheet variable	Sheet := ExcelApplication.WorkBooks[1].WorkSheets['my data'];

Why do we need to set the working worksheet into Sheet variable ? It is in order to avoid typing a long character string : ExcelApplication.WorkBooks[1].WorkSheets['my data'] to access the worksheet.

Go to Next Tutorial ( Setting Attributes of an Excel File )

Delphi Tutorial # 1

2010-03-30T22:22:00.000-07:00

Introducing Delphi

Delphi is an application development tool in Windows platform. Using this software you can build some Windows application. With visual approach, you can create application with some codes. Delphi based on Pascal Object language. If you are familiar with Pascal, it will be very easy to understand Delphi. But if you don’t know Pascal, you can learn both Delphi and Pascal in my tutorial at the same time.

There are some words that have to be clear before we start learning Delphi, such as application, form and component.

Application or application program is rows of codes to be done by computer. There are two kinds of application. Windows application and console application. Windows application is an application that runs under Windows. Non-Windows application, such as DOS application usually called console application. Generally, a Windows application has a form, but of course an application can have some forms. When we execute a form in a program, it will become a window.

A form usually contains some other components (a form is also a component). Label, button, edit box are components. Some components are visible. Label, button and edit box are visible components. The invisible component is called control. In Delphi, a project contains an application, and an application contains some forms.

Running the IDE

IDE or Integrated Development Environment is a part of Delphi where we can create our application. In IDE we can visually create a user interface and write some codes.

We can run the Delphi IDE from start menu. The main appearance of Delphi IDE shows a new project (project1) and a form (form1). Now we will see the Delphi IDE below :

- Main menu contains some menus (File, Edit, Search…etc)

- Toolbar contains some icons / tools.

- Form Window is where you design your interface visually

- Object Inspector contains two tabs : Properties and Events

- Component Palette contains components you can place in the form.

Changing Form Properties

An object has some characteristics. A person has name, age, weight etc. As an object, a form also has some characteristics : name, height, width, color etc.

You can change the properties of form through the object inspector. A form has fifty properties. But only some of them we often use. Now let’s change the name and the caption of our form from the object inspector, and see what happen to it :

Name : My_Form

Caption : My First Form

Why should we set a name for our form ? because if we have more than one form in our project, My_Form is more easily remembered rather than Form1, Form2…….

Saving Project

Now we’re going to save our first project by choosing File – Save All. You must create a new folder, ie : PracticingDelphi. After you create a new folder then give a unit name and project name.

And there will be some files saved in the folder :

.cfg : contains project configurations

.dof : contains project options (linker, compiler, searching directories etc)

.dpr : a project file

.res : contains standard windows resources

.dfm : a form file

.pas : a unit resources file (Pascal object codes)

Running Program

You can press F9 to run the program. And the result is only a blank windows, because we haven’t added anything to our form :

After we run the program Delphi create an executable file named MyProject.exe

Go to Next tutorial

Delphi - Interbase Tutorial # 7 : Modifying Query’s SQL Statement

2010-03-29T18:52:00.000-07:00

In the previous tutorial I have shared how to use a Query component. We can modify the SQL statement in a Query. Use the previous form. Add a Label component, two Edit components and a Database component. A Database component is used for data connection, so when we run the program, the login form will appear at the first place. Our form will be like this :

Set the properties of the new added components

Label1

Caption

Edit1

Text

"blank"

Edit2

Text

"blank"

Database1

AliasName	ALIASMYDATA
DatabaseName	MyDatabase

Change the DatabaseName property of the Query

Label1

DatabaseName

MyDatabase

Type the code below for the OnClick event of the GO button :

procedure TForm1.Button1Click(Sender: TObject);

begin

Query1.Close;

Query1.SQL.Clear;

Query1.SQL.Add

('Select * from EMPLOYEE');

Query1.SQL.Add

('where AGE >= :firstparameter');

Query1.SQL.Add

('and AGE <= :secondparameter');

Query1.Prepare;

Query1.Params[0].Value := StrToInt(Edit1.Text);

Query1.Params[1].Value := StrToInt(Edit2.Text);

Query1.Open;

end;

If you run the program and fill 32 in Edit1 and 35 in Edit2, you’ll get the result like this picture :

To modify the SQL statement in a Query component, first you have to deactivate the Query (Query1.Close;), clear the SQL statement (Query1.SQL.Clear;) and then you can add some SQL statement (Query1.SQL.Add(‘SQL statement’);). You can type SQL statement as much as you need. If you use parameters in the SQL statement, you can name the parameters with any meaningful names. In this example I name the first parameter with firstparameter and the second one with secondparameter. Then put the actual value into params() property of the Query. I put StrToInt(Edit1.Text) into params(0) and StrToInt(Edit2.Text) into params(1). You can also have parameters as much as you need. It begins with params(0).

Go to Previous Tutorial

Delphi - Interbase Tutorial # 6 : Query

2010-03-23T18:32:00.000-07:00

In Delphi, you can also use SQL to access your data. You have to use Query component that is in the Data Access Page of the component palette.

First, create a user interface like picture shown below :

Set the properties of the components

DataSource1

DataSet

Query1

Button1

Caption

&G O

DBGrid1

DataSource

DataSource1

Query1

DatabaseName	ALIASMYDATA
SQL	select * from employee where age >=30

You have to type the SQL code in the String List editor of Query component, see the picture below :

Type the code below for the OnClick event of the GO button :

procedure TForm1.Button1Click(Sender: TObject);
begin
Query1.Open;
end;

What is the meaning of Query1.Open ?

This statement activate the Query and execute the SQL statement in SQL property of Query1. The result is like the picture shown below :

You can also add an exit button into the user interface above.

Go to Previous Tutorial or Next Tutorial

Delphi - Interbase Tutorial # 5 : Create a user interface for manipulating table using DBEdit

2010-03-21T22:18:00.000-07:00

In the previous tutorial we created a user interface for manipulating table using DBGrid. Now we’re going to create one using DBEdit. We can use our previous program. Replace the DBGrid in the previous program with some labels and DBEdits, like the picture shown below :

Set the properties of the labels and DBEdits like tables below :

Label1

Caption

Label2

Caption

NAME

Label3

Caption

AGE

Label4

Caption

PHONE

DBEdit1

DataSource	DataSource1
DataField	ID

DBEdit2

DataSource	DataSource1
DataField	NAME

DBEdit3

DataSource	DataSource1
DataField	AGE

DBEdit4

DataSource	DataSource1
DataField	PHONENUMBER

Use the codes for the OnClick event of the buttons. Do not change the properties of Form, Table, DataSource and Buttons. Run the program, and now we can manipulate the ‘employee’ table using Buttons and DBEdits.

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Free Software for Learning HTML

2010-03-17T00:22:00.000-07:00

(Download Here)

When we learn HTML (Hyper Text Markup Language), we need a text editor, such as Notepad and a browser. Once we have finished writing some HTML codes, we save the codes in a file with .html extension. Then we run an internet browser to see if the codes run well or not. If it doesn’t, we go to the text editor and modify our HTML codes then try it in the browser again and so on. This makes me inconvenience. So I try to make it more convenient by creating a program that can free me from this to and fro situation.

Using this software we can get the result of HTML codes instantly by clicking RUN button. Type the HTML codes in the left window, and the result is in the right window.

type the HTML codes below, in the left window :

<html>
<head>
<p><a href="http://www.google.com">Google.com</a></p>
<p><a href="http://www.yahoo.com">Yahoo.com</a></p>
<p><a href="http://www.123codegenerator.blogspot.com">Download This Software Here</a></p>
</head>
<body>
</body>
</html>

then click Run to see the result

You can get this free software here

Delphi - Interbase Tutorial # 4 : Exception Handler

2010-03-09T16:49:00.000-08:00

In the previous tutorial, an error occur when you try to delete a record in ‘employee’ table. It is because of the ‘salary’ table refers to the record. An error message will appear. To avoid this, we’re going to create an exception handle.

Let’s see what kind of error will happen if we try to delete a record in ‘employee’ table. Run the program from Delphi IDE (not the executable file). You’ll see the error message below :

From the message, the exception that raised is EDBEngineError. Let’s see our code for OnClick event of Delete button. You have to add an exception handle code using TRY…..EXCEPT :

procedure TForm1.DeleteClick(Sender: TObject);
begin
try
Table1.Delete;
except
on EDBEngineError do
begin
MessageDlg('You can not delete this record because another table is currently using the data',
mtError,[mbOK],0)
end;
end;
end;

Then if you run the program and try to delete a record in ‘employee’ table that a record in ‘salary’ table refers to it, you’ll get a message like picture below :

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Delphi - Interbase Tutorial # 3 : Create a user interface for manipulating table without DBNavigator

2010-03-04T18:18:00.000-08:00

In the previous tutorial we have created a tiny user interface for manipulating table. Now we’re going to create a user interface without using a DBNavigator. If there is no DBNavigator, how do we manipulate our table ?. We’re going to use some buttons and codes to manipulate our table. Let’s see our blank form, add some components into it : a DBGrid, a Table, a DataSource, ten Buttons (Button1……Button10)

Set the properties of our components :

Form

Caption

EMPLOYEE TABLE

Table

Active	True
DatabaseName	ALIASMYDATA
TableName	EMPLOYEE

DataSource

DataSet

Table1

Button1

Caption	&First
Name	First

Button2

Caption	&Last
Name	Last

Button3

Caption	&Previous
Name	Previous

Button4

Caption	&Next
Name	Next

Button5

Caption	&Add
Name	Add

Button6

Caption	&Edit
Name	Edit

Button7

Caption	&Save
Name	Save

Button8

Caption	&Cancel
Name	Cancel

Button9

Caption	&Delete
Name	Delete

Button10

Caption	E&xit
Name	Exit

Now our form appears like the picture below :

Type the code for the OnClick event of the buttons :

procedure TForm1.ExitClick(Sender: TObject);
begin
Application.Terminate;
end;

procedure TForm1.FirstClick(Sender: TObject);
begin
Table1.First;{go to the first record}
end;

procedure TForm1.LastClick(Sender: TObject);
begin
Table1.Last;{go to the last record}
end;

procedure TForm1.PreviousClick(Sender: TObject);
begin
Table1.Prior;{go to the previous record}
end;

procedure TForm1.NextClick(Sender: TObject);
begin
Table1.Next;{go to the next record}
end;

procedure TForm1.AddClick(Sender: TObject);
begin
Table1.Append;{insert new record }
end;

procedure TForm1.EditClick(Sender: TObject);
begin
Table1.Edit;{edit existing record }
end;

procedure TForm1.SaveClick(Sender: TObject);
begin
Table1.Post;{save record }
end;

procedure TForm1.CancelClick(Sender: TObject);
begin
Table1.Cancel;{cancel record }
end;

procedure TForm1.DeleteClick(Sender: TObject);
begin
Table1.Delete;{delete record }
end;

To insert data we can use Table1.Append or Table1.Insert procedure. Find out yourself, the different between these two procedures.

Run the program. You can navigate and manipulating employee table by clicking the button. Notice that you can not delete any record in ‘employee’ table, because there another table that refers to ‘id’ column value of table employee. If you try to click Delete button, an error message will be appear :

In the next tutorial I will show you how to handle this exception.

Go to Previous Tutorial or Next Tutorial

Delphi - Interbase Tutorial # 2 : Create a user interface for manipulating table

2010-03-01T17:12:00.000-08:00

After we create an alias name for our database, we’re going to create a tiny user interface for manipulating and retrieving the tables in the database. Run Delphi from start menu, you’ll have a project with a form. Add a Button, a DBgrid, a DBNavigator, a Table and a DataSource.

Button component is in the Standard page of component palette. DBGrid and DBNavigator are in Data Controls page of component palette. Table and DataSource are in the Data Access page of component palette Then set the properties as the table shown below :

Form

Caption

EMPLOYEE TABLE

Button

Caption	&Exit
Name	Exit

Table

Active	True
DatabaseName	ALIASMYDATA
TableName	EMPLOYEE

DataSource

DataSet

Table1

DBGrid

DataSource

DataSource1

DB Navigator

DataSource

DataSource1

Now our form appears like the picture below :

Type the code for the OnClick event of Exit button :

procedure TForm1.ExitClick(Sender: TObject);
begin
Application.Terminate;
end;

Run the program. You can navigate and manipulate employee table using DBNavigator. To exit program click the Exit button.

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Delphi - Interbase Tutorial # 1 : Borland Database Engine

2010-02-26T20:15:00.000-08:00

Connecting Interbase Database Using BDE (Borland Database Engine)

Manipulating and retrieving a database using some SQL codes is such a nightmare for me. But it does not mean that my previous Interbase Tutorials are useless. For database programmer, knowing SQL is a must. But the users do not need to know about SQL.

Now, I am going to share how to create user interface for manipulating, retrieving and maintaining a database. We can use any development tools to create the interface, but in this tutorial I use Delphi.

Before we start working with Delphi, we have to make an alias of the database. There many method of connecting database, but we’re going to use BDE (Borland Database Engine). After we start BDE Administrator from start menu, the main window will appear :

You can start creating a new connection by choosing Object – New

Choose the Interbase as database driver, then press OK :

You’ll get an alias name INTERBASE1 (see the picture below)

You can rename the alias name. In this case we use the alias name : ALIASMYDATA

Fill in the SERVER NAME the location of our database : C:\mydata\MYDATA.GDB
And USER NAME : NEW_USER
If our database located in a remote computer, we have to put the computer / server name. Use slash not back slash : server_name:/mydata/MYDATA.GDB
Then click apply as the picture above.
Now we have an alias for MYDATA.GBD. The user interface we’re going to develop using Delphi have to be connected to the alias : ALIASMYDATA

To test the connection choose File – Diagnostics. The Communication diagnostic Tool window will appear. Type the password, then click Test. If the connection work, you’ll get the results message that InterBase Communication Test Passed!

Go to Previous Tutorial or Next tutorial

Stored Procedures ( Interbase Tutorial # 15 )

2010-02-26T18:33:00.000-08:00

Every programming language allows programmers to create procedures, if it doesn’t, we can call it a bad programming language. A stored procedure is a program to be stored in the database server. And it can be called or run manually by other program.

A stored procedure contains header and body. Header contains procedure name, input parameter(s) and output parameter(s). Body contains local variable(s) ( optional ) and a block of statements.

To be clear, let’s see the table below :

A Stored Procedure	Header	Procedure Name
		Input Parameter(s)
		Output Parameter(s)
	Body	Local Variable(s)
		A Block of Statements

The general syntax of a stored procedure is :

CREATE PROCEDURE procedure_name (input_variable(s) data_type(s))
RETURNS (output_variable(s) data_type(s))
AS
BEGIN
Local variable(s)
A block of Statements if procedure and trigger language
END

Example :

In the previous tutorial we have learnt how to retrieve data using SELECT. Let us review again how to get employee’s name whose age is above 27. The statement is :

select name from employee where age>27

The output is :

NAME
=============
Isaac Newton
Archimedes
Frank Borland
Max Planck

Now we can get same output, but this time we’re going to create a procedure. The procedure will be :

create procedure get_name (employee_age integer)
returns (employee_name char(30))
as
begin
for select name
from employee
where age > :employee_age
into :employee_name
do
suspend;
end

suspend send the value back to the calling application ( Interbase Windows ISQL )

Execute the procedure above in the SQL windows. Now execute this blow statement :

select * from get_name(27)

You’ll get the same output :

NAME
=============
Isaac Newton
Archimedes
Frank Borland
Max Planck

Using Local Variables

Let us modify the procedure above using a local variable

create procedure get_name_line (employee_age integer)
returns (line_number integer, employee_name char(30))
as
begin
   line_number = 0;
   for select name
   from employee
where age > :employee_age
into :employee_name
do
begin
line_number=line_number+1;
suspend;
end
end

after you execute the procedure, you can try this statement below :

select * from get_name_line(27)

The output is :

LINE_NUMBER EMPLOYEE_NAME
==============================
1 Isaac Newton
2 Archimedes
3 Frank Borland
4 Max Planck

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Access Privileges ( Interbase Tutorial # 14 )

2010-02-26T18:17:00.000-08:00

So far we have learnt how to develop a database. But only the owner of the database ( in this case NEW_USER ) and SYSDBA can access the database. Some other users may use the database. We can grant some privileges to these users, so they can retrieve or manipulate the table.

Before we start learning about access privileges, you need to create a new user. You can see how to create a new user in my first tutorial. Let’s name the new user OTHER_USER, and you can give any password you want for this user.

Now there are three users in your interbase server : SYSDBA, NEW_USER and OTHER_USER. SYSDBA can access the database created by NEW_USER, but OTHER_USER can’t. If you want OTHER_USER to retrieve or manipulate your database, you have to give some privileges to this user.

You can see the available access privileges in the table below :

SELECT	Read data
DELETE	Delete data
INSERT	Write new data
UPDATE	Modify existing data
REFERENCES	Create a table with a foreign key refers to the primary key
EXECUTE	Call stored procedures
ALL	SELECT, DELETE, INSERT, UPDATE and REFERENCES
ROLE	All privileges assigned to the ROLE

Giving Access privileges using GRANT

The syntax is :

GRANT privilege(s) ON table TO user

Example : We want to give SELECT privilege on ‘employee’ table to OTHER_USER, so OTHER_USER can retrieve the database. The statement will be :

grant select on employee to other_user

With Grant Option

We can use WITH GRANT OPTION clause to allow the user to give the privileges we’ve given to other users.

Example :

grant select, delete on employee to other_user
with grant option

Revoking Privileges

We can also revoke the privileges we’ve given to a user. The syntax is :

REVOKE privilege(s) ON table FROM user

Example : We want to revoke SELECT privilege on ‘employee’ table from OTHER_USER. The statement will be :

revoke select on employee from other_user

ROLE

If you want to give one or more privileges to some user using GRANT, you will type a lot of GRANT statement. You can create a ROLE to reduce the statement you type. A ROLE can contain one or more privileges. Follow these steps below to create and grant a ROLE to users :

- Define a ROLE
The syntax : CREATE ROLE role_name
- Inserting privileges to the ROLE
The syntax : GRANT privileges(s) ON table TO role_name
- Granting ROLE to users
GRANT role_name TO user(s)

Example :

create ROLE myrole

grant select, update, insert, delete on employee to myrole

grant myrole to other_user

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String Operator and Converting Uppercase ( Interbase Tutorial # 13 )

2010-02-21T17:25:00.000-08:00

String Operator

We can also join two or more character strings into a single string using string operator. The string to be joined can be the value of a column we retrieve, or we may add some character strings. The operator for joining some character strings is || .

Execute these some SQL statements below :

select name || ‘ is ’ || age || ‘ years old’ from employee

and we’ll get the data output :

==================================
Isaac Newton is 30 years old
Blaise Pascal is 25 years old
Archimedes is 32 years old
George Boole is 27 years old
Frank Borland is 31 years old
Max Planck is 28 years old

select ’Boolean Algebra is developed by ‘ || name from employee
where name=’George Boole’

the output is :

====================================
Boolean Algebra is developed by George Boole

select name || ‘ earns USD ‘ || totalsalary || ‘ per month’
from employee, salary
where id=employee_id

the output is :

================================
Isaac Newton earns USD 1100 per month
Blaise Pascal earns USD 2200 per month
Archimedes earns USD 3300 per month
George Boole earns USD 4400 per month

select ‘The highest salary is USD ‘ || max(totalsalary)from salary

the output is :

======================================
The highest salary is USD 4400

select ‘The total expense for salary is USD ‘ || sum(totalsalary) from salary

the output is :

================================================
The total expense for salary is USD 11000

Now you can try another combinations of some character strings.

Converting Uppercase

To convert character values to uppercase, we use UPPER function. When you create a domain, use CHECK constraint to ensure that the value you enter is always in uppercase.
If you want the value of ‘name’ column always in uppercase, the statement to create domain is :

CREATE DOMAIN string30 AS varchar(30)
CHECK (VALUE = UPPER (VALUE))

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Inner Join and Outer Join ( Interbase Tutorial # 12 )

2010-02-21T17:05:00.000-08:00

In Interbase you can join two or more tables. As a result of joining tables, Interbase will build a new table, which sometimes called ‘dynamic table’ or ‘virtual table’. Two kind of joins supported by Interbase : Inner Join and Outer Join.
Before we start to learn about Inner Join and Outer Join, execute these statement below :

insert into employee (id, name, age, phonenumber)
values ('5',’Frank Borland','31','555-9999')

insert into employee (id, name, age, phonenumber)
values ('6',’Max Planck’,'28','555-1199')

INNER JOIN

Inner join link rows in tables based on specified join conditions and return only those rows that match the join conditions. If a joined column contains a NULL value for a given row, that row is not included in the results table. Inner joins are the more common type because they restrict the data returned and show a clear relationship between two or more tables.

Example : You want to build a virtual table which contains two columns : id and total salary. The SQL statement is :

select a.name, b.salary from employee a inner join salary b
on a.id = b.employee_id

note :
a is correlation name or alias of ‘employee’ table
b is correlation name or alias of ‘salary’ table
you can make any alias name, ie : a, b, table1, table2, alias1, alias2....... etc

the output is :

NAME SALARY
========================
Isaac Newton 1000
Blaise Pascal 2000
Archimedes 3000
George Boole 4000

OUTER JOIN

Outer joins link rows in tables based on specified join conditions but return rows whether they match the join conditions or not. Outer joins are useful for viewing joined rows in the context of rows that do not meet the join conditions.

Example : You also want to build a virtual table which contains two columns : id and total salary. But this time you use OUTER JOIN. The SQL statement is :

select a.name, b.salary from employee a left outer join salary b
on a.id = b.employee_id

the output is :

NAME SALARY
============================
Isaac Newton 1000
Blaise Pascal 2000
Archimedes 3000
George Boole 4000
Frank Borland <>
Max Planck <>

Form the output of both examples above, you can see the difference between INNER JOIN and OUTER JOIN. OUTER JOIN returns NULL value rows, but INNER JOIN doesn’t.

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Adding Free Hit Counter to Your Blog or Website

2010-02-19T19:15:00.000-08:00

You can also view this post in Bahasa Indonesia

Sometimes we want to know how many visitors have visited our blog or website. It can be done by adding a hit counter. To add a hit counter to your blog or website, click here. You’ll be directed to hit-counter-download.com main page, see the picture below :

Choose one of the available hit counter. This page provide many kinds of hit counter :
- Basics Hit Counters
- Cool Hit Counters
- Digital Hit Counters
- Fancy Hit Counters

Then you’ll be directed to the submission form :

Fill the form, like picture above. Of course you need to enter your password. After you click Submit you’ll get HTML code that you can copy and paste into your blog or website

Retrieving Data from Two Table ( Interbase Tutorial # 11 )

2010-02-18T16:29:00.000-08:00

We already have two tables in our database. Each table contains some populations. Now let’s see what we have in each table using SELECT statement.

select * from employee

ID NAME AGE PHONENUMBER
==================================

1 Isaac Newton 30 555-5555
2 Blaise Pascal 25 555-1234
3 Archimedes 32 555-2233
4 George Boole 27 555-4521

select * from salary

SALARY_ID EMPLOYEE_ID SALARY BONUS TOTALSALARY
=======================================================

1 1 1000 100 1100
2 2 2000 200 2200
3 3 3000 300 3300
4 4 4000 400 4400

Now we’re going to get employee’s name and their total salary. It will be a little bit complicated, because the ‘name’ column is in ‘employee’ table and the ‘totalsalary’ column is in ‘salary’ table. But don’t be worry, we can also retrieve data from two table using SQL statement. And the statement is :

select name, totalsalary from employee, salary
where employee.id = salary.employee_id

The output is :

NAME TOTALSALARY
========================

Isaac Newton 1100
Blaise Pascal 2200
Archimedes 3300
George Boole 4400

The WHERE clause is for comparing the value of ‘id’ column in ‘employee’ table with the value of ‘employee_id’ in ‘salary’ table.

Now we’re going to get names and their total salaries of employee whose age is 30 year above. The statement will be :

select name, totalsalary from employee, salary
where age>=30 and employee.id = salary.employee_id

The output is :

NAME TOTALSALARY
=========================

Isaac Newton 1100
Archimedes 3300

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facebook widget

2010-02-16T21:02:00.000-08:00

Adding a Facebook Widget to your Blog/Web

You can also view this post in Bahasa Indonesia

It’s quite simple to add a FaceBook Widget to your blog or website. Just follow these steps below :

1. From your profile click Create a Profile Badge text link

2. You can edit your badge by clicking Edit this badge

3. You can choose the displayed items on your badge by checking them in the list. Then click save.

4. If you have a Blogspot or TypePad account, you’ll be directed to the page. If you click other, you’ll get the code. You can copy and paste the code to wherever you want.

Subquery and Aggregate function ( Interbase Tutorial # 10 )

2010-02-16T19:54:00.000-08:00

Subquery

In a WHERE clause, you have a column, a comparative operator and a value to be compared with the column. Subquery provide a value from the other table that will be compared with the column you have in a WHERE clause. In some case we need a subquery for retrieving data.

For example, we want to get a name who earns 3300 a month. The problem is, we don’t have ‘name’ column in the ‘salary’ table. In this case we have to use subquery to get a value to be compared.

In ‘salary’ table we have ‘employee_id’ column which has a constraint value that refers to ‘id’ column in ‘employee’ table. Fist, we have to get an employee_id who earns 3300 from ‘salary’ table, then we compare the employee_id with ‘id’ column in ‘employee’ table to get a name. and the SQL statement will be :

select name from employee

where id = (select employee_id from salary where totalsalary=3300)

and the output will be :

NAME
==============================

Archimedes

Now, I will give you a problem :
We want to get the total salary of the employee whose phone number is 555-1234.
Figure out the SQL statement to solve this problem !

Aggregate Function

SQL provide some aggregate functions that calculate some values in columns. There are five aggregate functions that provided by SQL :

AVG
Get the average value in a group of rows

COUNT
Count the number of rows. You can use WHERE clause here to specify the rows you count

MIN
Get the minimum value in a group of rows

MAX
Get the minimum value in a group of rows

SUM
Adds numeric values in a group of rows

Some examples of using aggregate function :

select avg(age) from employee

select avg(totalsalary) from salary

select min(salary) from salary

select count(totalsalary) from salary where totalsalary>2000

select sum(totalsalary) from salary

You can try other SQL statement using aggregate functions.

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Search Condition ( Interbase Tutorial # 9 )

2010-02-15T17:24:00.000-08:00

NOT

You can use NOT if you want to retrieve data which value is not equal to the condition. The syntax is :

SELECT column FROM table
WHERE NOT column = value

The other way to get the same data is :

SELECT column FROM table
WHERE column != value

Example 1 : we want to retrieve all data except data which age is above or equal to 30.

select * from employee where not age<30

the statement above will have the same output with this statement below :

select * from employee where age>=30

Example 2 : we want to retrieve data except the data which name is Archimedes.

select * from employee where name!=’Archimedes’

LIKE

LIKE is used for retrieving data which has a particular matches with the pattern condition you give. The syntax is :

SELECT column FROM table
WHERE column LIKE ‘%pattern’

Example 3 : we want to retrieve data which name is ended with a particular pattern ‘ton’

select * from employee where name like ‘%ton’

Example 4 : we want to retrieve data which name has a particular pattern ‘chi’ in the middle.

select * from employee where name like ‘%chi%’

Example 5 : we want to retrieve data which name is started with a particular pattern ‘Ge’

select * from employee where name like ‘Ge%’

STARTING WITH

You can use STARTING WITH if you want to retrieve data which column’s value started with a pattern. The syntax is :

SELECT column FROM table
WHERE column STARTING WITH pattern

Example 6 : we want to retrieve data which name is started with ‘Bla’

select * from employee where name STARTING WITH ‘Bla’

it will have same output with the statement below :

select * from employee where name like ‘Bla%’

CONTAINING

You can use CONTAINING to retrieve data which contain a value. The syntax is :

SELECT column FROM table
WHERE column CONTAINING value

Example 7 : we want to retrieve data which name contains ‘s’ letter

select * from employee where name containing ‘s’

BETWEEN and IN

BETWEEN is for retrieving data within a range value. The syntax is :

SELECT column FROM table
WHERE column BETWEEN value1 AND value2

The statement below will get the data which name is started with a letter between C and J.

select * from employee where name between ‘C’ and ‘J’

IN is for retrieving data with several values to be compared. The syntax is :

SELECT column FROM table
WHERE column IN (value1, value2, value3…….)

The statement below will get the data which age is 25, 27 or 32

select * from employee where age in (‘25’,’27’,’32’)

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Retrieving Data ( Interbase Tutorial # 8 )

2010-02-14T16:53:00.000-08:00

Now we’re going to populate our database again. To avoid typing the SQL statement and executing them one by one in the Interbase Windows ISQL, type these SQL statements below in a text editor :

connect 'c:\mydata\mydata.gdb'
user 'NEW_USER' password 'password';

insert into employee (id, name, age, phonenumber)
values ('1','Isaac Newton','30','555-5555');

insert into employee (id, name, age, phonenumber)
values ('2','Blaise Pascal','25','555-1234');

insert into employee (id, name, age, phonenumber)
values ('3','Archimedes','32','555-2233');

insert into employee (id, name, age, phonenumber)
values ('4','George Boole','27','555-4521');

insert into salary (salary_id, employee_id, salary, bonus)
values ('1','1','1000','100');

insert into salary (salary_id, employee_id, salary, bonus)
values ('2','2','2000','200');

insert into salary (salary_id, employee_id, salary, bonus)
values ('3','3','3000','300');

insert into salary (salary_id, employee_id, salary, bonus)
values ('4','4','4000','400');

(note : if you type SQL statements in a text editor, you have to put a ‘;’ at the end of each statement)

Save the statements above in a file named ‘inputdata.txt’. Then execute it in the Interbase Windows ISQL by choosing File – Run an ISQL Script.

After populating our database, now we’re going to get the data out and use them. To get the data out we use SELECT statement. The SELECT statement is the most important, because if we have a data structure but we can not get them out and use them, it will be useless. The syntax is :

SELECT column1,column2…. FROM TableName

or

SELECT * FROM TableName

SELECT statement has six keywords : DISTINCT, FROM, WHERE, GROUP BY, HAVING and ORDER BY.

WHERE clause

WHERE clause will limit the retrieved rows with specified conditions. Only the rows which has the specified conditions will be retrieved. The syntax is :

SELECT column1,column2…. FROM TableName
WHERE condition

Execute these statements below and see what happen in the output windows :

select * from employee where age>=30

select name, phonenumber from employee where age>=30

select name, phonenumber from employee where not age>=30

select name, phonenumber from employee where (age>=30) and (id>1)

select * from employee where (age>30) or (age<26)

ORDER BY clause

ORDER BY clause will order the output of a SELECT statement by the specified column. OERDER BY has a syntax :

ORDER BY column ASC

or

ORDER BY column DESC

Execute these statements below and see what happen in the output windows :

select * from employee order by age asc

select * from employee order by age desc

select * from employee where age <>

DISTINCT clause

DISTINCT clause will eliminate duplicate rows of the output of a SELECT statement. The syntax is :

SELECT DISTINCT column FROM table

GROUP BY

GROUP BY clause will group rows according the value of specified column. The syntax is :

SELECT column FROM table GROUP BY column

HAVING clause

Having clause will specify search condition and to use with GROUP BY clause. The syntax is :

SELECT column FROM table GROUP BY column HAVING search_condition

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Primary Key, Foreign Key, Constraint ( Interbase Tutorial # 7 )

2010-02-12T20:57:00.000-08:00

Every table must have a primary key. Only one primary key can be created in a table. But we may have a collective combination of some columns to form a primary key. Primary key has to be a column which has a unique value. In our case, ‘employee’ table also must have a primary key. The column which has a unique value is ‘id’ column.
The better way to create ‘employee’ table with a primary key is :

(Note : before you execute the SQL codes below, you have to drop your previous table in the database)

create table employee(
id domain_id not null primary key,
name string30 not null,
age domain_age not null,
phonenumber string12 not null);

a table can also has a foreign key. Foreign key is a column or a combination of some columns in a table. The value must refer to the primary key which is in the table or other table. Now we’re going to create a table which has a foreign key refers to the primary key of ‘employee’ table.

create table salary(
salary_id domain_id not null primary key,
employee_id domain_id not null,
salary integer not null,
bonus integer not null,
totalsalary computed by (salary+bonus),
constraint fk1 foreign key (employee_id) references employee(id));

(note : fk1 is the name of the constraint)

now we have a better database than our previous. We can see what is in our database by choosing Metadata - Extract Table. And the output is :

/* Extract Database D:\mydata\MYDATA.GDB */
CREATE DATABASE "D:\mydata\MYDATA.GDB" PAGE_SIZE 1024
;

/* Domain definitions */
CREATE DOMAIN STRING30 AS VARCHAR(30);
CREATE DOMAIN STRING12 AS VARCHAR(12);
CREATE DOMAIN DOMAIN_ID AS INTEGER
check(value>0);
CREATE DOMAIN DOMAIN_AGE AS INTEGER
check(value>18 and value<55);>/* Grant permissions for this database */

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Modifying Table and Computed Column ( Interbase Tutorial # 6 )

2010-02-09T16:03:00.000-08:00

You can modify your table using ALTER TABLE statement. With this statement you can add a columns into your table or you can delete a column as well. The syntax of this statement is :

For adding a column :

ALTER TABLE TableName ADD columnname datatype

For dropping a column :

ALTER TABLE TableName DROP columnname

Example 1 : in ‘employee’ table, we have four columns : id, name, age and phonenumber. We’re going to delete age column and add a column named bithdate.
First we delete age column using this statement :

Alter table employee drop age

Age column has been dropped. Now we’re adding birthdate column using this statement :

Alter table employee add birthdate date

We use date data type for birtdate column. Now we have four column in ‘employee’ table : id, name, phonenumber, birthdate.

To see the changes we've made in 'employee' table, choose Metadata - Extract Table. And the output is :

/* Extract Table EMPLOYEE */

/* Table: EMPLOYEE, Owner: NEW_USER */
CREATE TABLE EMPLOYEE (ID INTEGER NOT NULL,
NAME VARCHAR(30) NOT NULL,
PHONENUMBER VARCHAR(12) NOT NULL,
BIRTHDATE DATE);

Computed column

We can also have a column that has a value based on the values of other columns in the table. The syntax to create a computed column is :

ColumnName COMPUTED BY ( arithmetic operation )

Example 2 : in ‘employee’ table we’re going to add three columns : salary, bonus, totalsalary. And the totalsalary column’s value = salary column’s value + bonus column’s value.

The statement will be like this :

Alter table employee add salary integer

Alter table employee add bonus integer

Alter table employee add totalsalary computed by (salary+bonus)

You have to execute the statements above one by one in the InterBase Interactive SQL window. Now we have ‘employee’ table which has seven columns : id, name, phonenumber, birthdate, salary, bonus and totalsalary.
To see what we have in mydata.gdb database choose Metadata – Extract Database. And the output is :

/* Extract Database D:\mydata\MYDATA.GDB */
CREATE DATABASE "D:\mydata\MYDATA.GDB" PAGE_SIZE 1024
;

/* Domain definitions */
CREATE DOMAIN STRING30 AS VARCHAR(30);
CREATE DOMAIN STRING12 AS VARCHAR(12);
CREATE DOMAIN DOMAIN_ID AS INTEGER
check(value>0);
CREATE DOMAIN DOMAIN_AGE AS INTEGER

check(value>18 and value<55);

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Domain ( Interbase Tutorial # 5 )

2010-02-05T18:09:00.000-08:00

What is Domain ?

Let us see our SQL script in the previous tutorial for creating table ‘employee’ :

create table employee(
id integer not null,
name varchar(30) not null,
age integer not null,
phonenumber varchar(12) not null)

We have an integer data type for column ‘id’ and ‘age’. As we know integer has range value between -2,147,483,648 to 2,147,483,647. We can insert a negative value to these columns. But in the real world, id and age can not have a negative value.
We can solve this problem by creating a DOMAIN. DOMAIN is a customized column definition.

The syntax to create a domain is :

CREATE DOMAIN domain_name AS data type
DEFAULT devault_value NOT NULL
CHECK (condition)

DEFAULT clause and CHECK clause are optional.

Type the codes below in the text editor, and save it with file name ‘mydata_domain.txt’.

create database 'c:\mydata\mydata.gdb'
user 'NEW_USER' password 'password';

create domain string30 as varchar(30);
create domain string12 as varchar(12);
create domain domain_id as integer check(value>0);
create domain domain_age as integer
check(value>18 and value<55);

Go to InterBase Interactive SQL window.

You can not run the script above, because database 'c:\mydata\mydata.gdb' is slready exist. You need to drop the old database first.

Connect to the old database, then choose File – Drop Database. So the old database ‘c:\mydata\mydata.gdb' is now deleted. Then you run the script above by choosing File – Run an ISQL Script. And choose your ISQL script file : ‘mydata_domain.txt’. Now you have a better column definition in your table ‘employee’.

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Inserting, Reading, Updating and Deleting Data ( Interbase Tutorial # 4 )

2010-02-04T19:35:00.000-08:00

We already have a database ‘mydata.gdb’, and it contains a table ‘employee’. Now we’re going to populate our database.

Inserting Data

The syntax for inserting data into a table is :

INSERT INTO TableName (field1,field2,field3,….)
VALUES (‘value1’,’value2’,’value3’,…)

Go to the Interbase Windows ISQL from the start menu. Connect to your database. Insert first record into your table ‘employee’ by typing these SQL codes in the SQL statement area :

insert into employee (id, name, age, phonenumber)
values ('1','Isaac Newton','30','555-5555')

then execute the codes. Now you have your first record in your table :

Id : 1
Name : Isaac Newton
Age : 30
Phonenumber : 555-5555

Now insert records below into your table ‘employee’ with the same way :

Id : 2
Name : Blaise Pascal
Age : 25
Phonenumber : 555-1234

Id : 3
Name : Archimedes
Age : 32
Phonenumber : 555-2233

Id : 4
Name : George Boole
Age : 27
Phonenumber : 555-4521

You have to type the same SQL codes for each record. If you’ve got hundreds of records, it will be a nightmare to do this. And I won’t do this. Of course there is more civilized way to do this. Soon I will share how to create a “user friendly interface”.

Reading Data

We have four records in our table, now we’re reading the record using this syntax :

SELECT column1,column2…. FROM TableName

If you want to read all columns of your records, the syntax is :

SELECT * FROM TableName

Example1 : if you want to read all columns in table ‘employee’ the code will be

select * from employee

Example2 : If you only want to read column ‘name’ and ‘age’ of your table, the codes will be

select name, age from employee

Updating Data

If you want to update your data in the table use this syntax :

UPDATE TableName
SET column = value
WHERE condition

WHERE is optional. If there’s no WHERE, all the records will be updated. Otherwise, it will make restrictive change to the record which is in the condition.

Example 3 : You want to increase all ages of your record by 1

update employee set age = age + 1

Example 4 : If you want to change Archimedes’ phone number, you have to use WHERE clause

update employee set phonenumber = ‘555-7777’
where name=’Archimedes’

Deleting Data

To delete data from your table use this syntax :

DELETE from TableName
WHERE condition

If there is no WHERE clause, all the record will be deleted from the table. If you use WHERE clause, only a record which has the condition will be deleted.

Example 5 : You want to delete employee whose age is above 30

delete from employee where age > 30

Committing Your Work

After you execute some SQL codes, you need to commit your work. If you don’t, other users won’t see the changes you have made. Commit your work by choosing File – Commit work.

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Creating a Database ( Interbase Tutorial # 3 )

2010-02-02T20:58:00.000-08:00

What is database ?

A database is like a container. You have some tables in the container. Each table related to others with some special ways, so the owner of the database can easily maintain or manipulate the tables.

To create new database we have to run InterBase Windows Interactive SQL from the start menu.

Choose Create database, then the Create Database Window appears.

Enter your database name, for example : c:\mydata\mydatabase.gdb
Enter your username and password then press OK.

Now you’ve got a database named ‘mydatabase.gdb’ in folder ‘mydata’ , but you haven’t got any tables in it.

Creating a table

A table always has some rows and columns. Where each row represent each record of your table and each column represent each field of your record.

For example

a record of the table above has four fields : ID, Name, Age and PhoneNumber

To create a table in interbase, you have to write some Structured Query Language (SQL) codes in the InterBase Interactive SQL window. The SQL codes to create the table above is shown below :

create table employee(
id integer not null,
name varchar(30) not null,
age integer not null,
phonenumber varchar(12) not null)

then execute your codes.
Now, see each field we have in the table ‘employee’ :

fields data type
id integer
name string (has maximum character = 30)
age integer
phonenumber string (has maximum character = 12)

‘not null’ means that each field must have a value

Now you already have a database contains a table named ‘employee’. You can create another table with the same way. The number of table depends on your need.

Creating a Database Using Text Editor

Another way to create a database, you can type your SQL codes in a text editor (ie : notepad) before you execute them in InterBase Interactive SQL window.

Type these SQL codes in the text editor, then save it with a name : ‘mydata.txt’.

create database 'c:\mydata\mydata.gdb'
user 'NEW_USER' password 'password';

create table employee(
id integer not null,
name varchar(30) not null,
age integer not null,
phonenumber varchar(12) not null);

Go to the InterBase Interactive SQL window and execute the codes by choosing File – Run an ISQL script. And choose your ISQL script file : ‘mydata.txt’. If your SQL script has no errors, the database ‘mydata.gdb’ will be created and it contains a table ‘employee’.

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Changing the SYSDBA default password ( Interbase Tutorial # 2 )

2010-02-01T18:18:00.001-08:00

You can also see this post in Bahasa Indonesia

In the previous tutorial, we have learnt to create a new user. The default password that we use to log in is ‘masterkey’. It is the default password of super user SYSDBA.

Now, we are going to change this default password using our own. Because everyone can be easily connected to your database, and may do some harmful actions to your database, if we are still using the default password.

First, we have to run the command prompt from the start menu. Go to the directory where the executable file ‘gsec.exe’ located. It is usually located in :

C:\Program Files\InterBase Corp\InterBase\bin>

See the picture below

Then we need to log in using SYSDBA and the default password. Type this command :

gsec –user sysdba –password masterkey

change the password using this command :

modify sysdba –pw newpassword

The default password now has been changed with the new one : ‘newpassword’
Type ‘quit’ to exit the program.

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Creating a New User in Interbase ( Interbase Tutorial # 1)

2010-01-31T21:16:00.000-08:00

In this first tutorial, I want to share how to create a new user using interbase 5.0 (in interbase 6.0 is quite the same). First, you have to make sure that the interbase server has been installed to your computer. It will run automatically when you turn on your computer. If it doesn’t, then you need to run the interbase guardian manually by choosing the icon from the start menu.

Starting the interbase server manager

Run the interbase server manager from the folder on start menu. Then the interbase sever manager form will appear as the picture shown below.

Logging in interbase server

First you need to log in to the local interbase sever. Choose File – Server Login as the picture shown below.

Then the interbase login form will appear

Input the user name : SYSDBA. It is the default user. Type the password : masterkey. Then press OK.
After you log in, the interbase server manager will show the connection and the server summary.

The picture shows that you have been connected to the local server, and the user being connected is SYSDBA

Creating a new user

To start creating a new user, choose Tasks – User Security as the picture shown below.

Then the interbase security form will appear

then click Add User

Type your new user name. Type and re-type your 8 character password. If you type more than 8 characters, the rest of them will not be used. Then click OK. A new user has been created as shown below.

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