Re: Conditional Trigger

mowinom_at_hotmail.com wrote:
> Hello all,
>
> I have the following task: I have a table with two fields, ISBN
> (NUMBER 9), TITLE and PERIODICAL_OWNER (NUMBER 9). I am trying to
> create a trigger that checks on insert, that the ISBN being entered is
> not already in the table but if it does, it must exist in the
> PERIODICAL_OWNER column.
>
> So, if the new ISBN being entered is already in the table, it has to
> be in the PERIODICAL_OWNER column in order for it to be accepted. I am
> new to PL/SQL and have tried writing a trigger but it's not working.
> Here it is:
>
> IF :New.ISSN = :Old.ISSN And
> :New.ISSN NOT IN (:Old.Tidsskriftnr_eier) THEN
> RAISE_APPLICATION_ERROR(-20070, 'ERROR>>' ||
> ' PERIODICAL:' ||
> ' For ISSN that already exists in the basen, it' ||
> ' must exist in periodicald to be accepted.');
> ELSE
> :New.ISSN := :New.ISSN;
> END IF;
>
> Thank you in advance for your help
>
> --
> Me

Ever heard of modeling and normalization?

You have two tables: ISBN is a primary key (which will guarantee uniqueness of ISBN numbers) on the first, and your second table has Periodical as PK, and a foreign key relation to ISBN (mandatory).

Really! second class, before Xmas!

-- 
Regards,
Frank van Bortel

Top-posting is one way to shut me up...