Question

So, I’m trying to create a trigger that will throw an error on inserting data if a foreign key code is not valid. I have two tables, Publisher and Title. Title has a publisher code on it, as does Publisher. I have the trigger on my Title for insert, and I am currently doing an if not exists and selecting the Publisher row where the code is equal to the inserted row’s publisher code. I don’t know if this is the right way to do it, and probably not, as SQL is giving me a “multi-part identifier Inserted.PublisherCode could not be found” error. Any help you guys could give would be appreciated. Thanks.

go
create trigger TR_Title_PublisherCode_Insert
on title
for Insert
as
    if not exists(select * from Publisher where PublisherCode = Inserted.PublisherCode)
    begin
        raiserror('Publisher does not exist', 16, 1)
        rollback tran
    end

Answer 1

INSERTED and DELETED are table too

So you have to do this:

if not exists(
    select * from Publisher 
    where PublisherCode in (SELECT PublisherCode FROM inserted) 
)

By the way, as hkf said, if you identified PublisherCode AS foreign key, you won’t have a need to make trigger