Pattern search + Shift AND Algorithm

Hello, I am confronted with a usual problem in database applications: I have to prevent the users from inserting items more than once. The primary key of this item is a text string, therefore my first choice was the Shift-AND algorithm by S.Wu and U. Manbar to find rows with a similar key before entering a new one. We use Informix Online and the problem now is: how can do a select statement based on the above algorithm ? The search features of SQL (LIKE or MATCHES) cannot solve the problem. Is there any way of hooking into the where clause evaluatation ? If I cannot do this I see only these two alternatives: - forget the Shift-AND alg. and use weaker similarity-conditions using MATCHES and secondary keys of the item which would be more work with less outcome with respect to finding similiar itesm or - read all the primary keys first and do the check by myself which would cost a considerable amount of performance. I cannot believe I am the first with this problem. Any help or hints are very appriciated. Thanks in advance Michael __________ _/_/_/_/_/ _/_/_/_/ _/_/_/_/ Michael Jatzeck michel@taz.de _/ _/ _/ _/ die tageszeitung _/ _/_/_/_/ _/ Germany _/ _/ _/ _/ D-10969 Berlin Phone: +49-30-25902-? _/ _/ _/ _/_/_/_/ Kochstr. 18 FAX : +49-30-2510694