SQL Triggers

Question

Hi everyone,
I'm hoping someone could help me here without sledging me or referring to name calling like 'n00b'. I admit I am new with SQL, but a way to learn is to ask questions...so...
I'm stuck on a query in which I have to write a trigger that will implement an 'update cascade referential integrity rule' between any 2 tables in a database.
The two tables I have chosen are Charter and Charter Leg.
Basically, what I want the trigger to do is to change CHARTER_NBR in Charter Leg when I modify CHARTER_NBR in Charter.
CHARTER_NBR is a PK in Charter and a FK in Charter Leg.
This is what I've come up with so far:
CREATE OR REPLACE TRIGGER Upd_Cas_01
BEFORE UPDATE OF charter_nbr ON Charter
FOR EACH ROW
BEGIN
     UPDATE           Charter_leg
     SET           charter_nbr = new.charter_nbr
     WHERE          charter_nbr = old.charter_nbr
     DBMS_OUTPUT.PUT_LINE ('Corresponding Charter Number in the Charter Leg table has also been updated');
END;
Output:
TRIGGER Upd_Cas_01 Compiled.
UPDATE Charter
SET charter_nbr = 999
WHERE charter_nbr = 1;
Output:
Error starting at line 1 in command:
UPDATE Charter
SET charter_nbr = 999
WHERE charter_nbr = 1
Error at Command Line:1 Column:7
Error report:
SQL Error: ORA-04098: trigger 'UPD_CAS_03' is invalid and failed re-validation
I hope someone can help me out. Thanks.

Answer 1

thanx for the help guys...eventually solved it in the end...not really sure how, but i played around with my existing code and it finally compiled without an error.
the last trigger i need to write now is pretty complex and i doubt i can explain it properly, but here goes:
-checks when an Employee is allocated to a Charter, they are qualified,
and
-when a Helicopter is allocated, it is suitable for the Charter.
it basically has to be one HUGE trigger...wish me luck -_-
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