Whenever we commit after entering data in Oracle Forms, many triggers fires during this event and also 

 fires just before inserting or updating the record into table. We can write Pre-Update and Pre-Insert triggers on particular block to just allow the process or to stop the process by using "Raise Form_Trigger_Failure" command, the following are the some examples:

 

Suppose you have a data block and there is a field which need to be validate just before inserting the record, then you must write the Pre-Insert trigger for this purpose, below is an example:

 

Declare

v_avl_qty number;

Begin

   Select avl_qty into v_avl_qty

     From stock_inhand

    Where Item_Code = :Block1.item_code;

if v_avl_qty < :Block1.qty_issued then

Raise Form_Trigger_Failure;

--- Execution stopped...

end if;

--- Else insertion will take place...

End;

And now I am giving you another example, suppose there is a field which need to be assigned from database just before the updation of the record, then you must write a Pre-Update trigger for this purpose, below is an example:

Declare

   v_value varchar2(10);

Begin

   Select a_value into v_value

     From a_table

    Where b_value = :Block1.b_value;

--- Assign this value to block item

:Block1.a_value := v_value;

--- you can assign any others value to any field just before updation or insertion like:

:Block1.create_date := Sysdate;

Exception

  when others then

     --- After any error or no data found you still want to continue then you can use only Null; statement

     Null;

     --- and any other value to any field you can still assign

:Block1.create_date := Sysdate;

End;

See also: