Database Constraints in Forms:-

The following example helps to learn creating data block manually.

Example
Create dept table in your database.

SQL>  CREATE TABLE DEPT (DEPTNO NUMBER(2),
DNAME VARCHAR2(14),
LOC VARCHAR2(13) );

 

Insert four rows into the table.

SQL> INSERT INTO DEPT VALUES (10, 'ACCOUNTING', 'NEW YORK');
SQL> INSERT INTO DEPT VALUES (20, 'RESEARCH', 'DALLAS');
SQL> INSERT INTO DEPT VALUES (30, 'SALES', 'CHICAGO');
SQL> INSERT INTO DEPT VALUES (40, 'OPERATIONS', 'BOSTON');
SQL> commit;

SQL> Select * from dept;

Open the form builder tool
You will get welcome to Form builder Select build new form manually Ok
You will be directed to object navigator.

Select data blocks click on create button.

 

 

 Build new data block manually Ok  ( Empty block is created ).
Create canvas
Select Canvases Click on create button ( Canvas is created ).
Go to Layout Editor ( Tools Layout Editor )

Place three text item on the layout.
For each text item, provide the following properties

Properties	1st text item	2nd text item	3rd text item
Name	DEPTNO	DNAME	LOC
Datatype	Number	Char	Char
Column Name	deptno	dname	loc
Prompt	Deptno	Dname	Loc

In object Navigator select the block, provide the following properties

Name	DEPT
Query data source name	Dept
Query data source column	column name	datatype	length
	DEPTNO	NUMBER	2
	DNAME	VARCHAR2	14
	LOC	LOC	13

File Save
Program Compile Module
Program Run form

Click on execute query