How to create a sequence for an particular item in my apex form

Question

Hi friends,
I created an database application, of a form with a report, and it is working fine...
But in my form, i have a requirement....The below are the existing fields in my form
issue no
created by
start date
status
priority
due date
Among these fields in my form i need to create a 'Sequence' for my field "issue no",
So that whenever i opened the form the 'issue number' must generate automatically like 1 for the first time, 2 for the second time and so on..
For that i created a sequence
CREATE SEQUENCE "ORDERS_SEQ"
MINVALUE 1
MAXVALUE 999999999999999999999999999
INCREMENT BY 1
START WITH 1000
NOCACHE
NOCYCLE;
But for validation where i need to write the sequence query for the particular item 'issue no'....i dont have any idea of where to write the validation query for the sequence..
please tell where i need to write in step wise manner..please help me friends...
As the below is my validated sequence query for item 'issue no'
'select seq.issue_id.nextval into issue_no'
This is my above validation query whether the query that i mentioned is right..if not let me know the validation query..
And also i need where to apply this validation query in steps..
Thanks in advance
Regards,
Harry...

Answer 1

Harry,
Rik is on the right track. Here is a sample insert trigger: Would need to substitute you sequence ORDERS_SEQ with my sequence las_log_seq, how you define or use timestamps is up to you.
DROP TRIGGER LASDEV.BINS1_LAS_LOG_TBL;
CREATE OR REPLACE TRIGGER LASDEV."BINS1_LAS_LOG_TBL"
   BEFORE INSERT
   ON las_log_tbl
   FOR EACH ROW
BEGIN
   -- Description: Insert log_seq, creation_dt, creation_id,
   --              lst_updt_dt and lst_updt_id.
   -- Maintenance:
   -- Date        Actor          Action
   -- ====        =====          ======
   -- 07-Sep-2010 J. Wells       Create.
   :new.creation_id := nvl( v( 'app_user' ), user );
   :new.creation_dt := SYSDATE;
   :new.lst_updt_dt := :new.creation_dt;
   :new.lst_updt_id := :new.creation_id;
    SELECT las_log_seq.NEXTVAL
      INTO :new.las_log_seq
      FROM DUAL;
END bins1_las_log_tbl;
/Heff