Question

Hi guys I need to create a trigger in ORACLE 10g which ensures that a deathDate that is BEFORE the birthDate cannot be entered. I am really struggling on this please can you provide support thank you kind people.

My scheme is:

Actor (actorID, lastName, firstName, middleName, suffix, gender, birthDate, deathDate)
Movie (movieID, title, year, company, totalNoms, awardsWon, DVDPrice, discountPrice)
Quote (quoteID, quote)
Role (roleID ,roleName ,gender ,actorID* ,movieID*) 
RoleQuote (roleID*, quoteID*)

Thank you

If there is any more information that you require please ask

My relationship constraint are:

CONSTRAINT_NAME                C                                                
------------------------------ -                                                
QUOTE_FK                       R                                                
ROLE_FK                        R                                                
MOVIE_ROLE_FK                  R                                                
ACTOR_ROLE_FK                  R                                                
ACTORID                        P                                                
MOVIEID                        P                                                
QUOTEID                        P                                                
ROLEID                         P                                                
ROLEQUOTEID                    P       

Relationships:

ALTER TABLE Role ADD CONSTRAINT ACTOR_ROLE_FK FOREIGN KEY (actorID) REFERENCES Actor (actorID);
ALTER TABLE Role ADD CONSTRAINT MOVIE_ROLE_FK FOREIGN KEY (movieID) REFERENCES Movie (movieID);
ALTER TABLE RoleQuote ADD CONSTRAINT Role_FK FOREIGN KEY (roleID) REFERENCES Role (roleID);
ALTER TABLE RoleQuote ADD CONSTRAINT Quote_FK FOREIGN KEY (quoteID) REFERENCES Quote (quoteID);

Answer 1

That sort of constraint should be implemented as a CHECK constraint

ALTER TABLE actor
  ADD CONSTRAINT chk_birth_before_death CHECK( birthDate < deathDate );

If you really need the constraint to be enforced with a trigger (this will be slower and require more work)

CREATE OR REPLACE TRIGGER check_death_date
  AFTER INSERT OR UPDATE ON actor
  FOR EACH ROW
BEGIN
  IF( :new.birthDate > :new.deathDate )
  THEN
    RAISE_APPLICATION_ERROR( -20001, 'Birth date cannot be later than death date.' );
  END IF;
END;