Trigger: Insert if not exists?

Hi,
I am trying to devise a trigger that inserts an object_id and a list of the object's title_words into a title_words table. I would like to avoid duplicate rows by ensuring that, even if the same title_word occurs many times, only one insert for that object_id/title_word pair will occur. Is there a simple way to do this?
 [Oracle 8i, PL/SQL]
 Thx in Advance,
 Barry Prentiss
 Stanford University Received on Tue Dec 10 2002 - 13:38:00 CST