While it is true that SQL Server must do a physical lookup to verify that the value of the FK is in the parent table, you usually don't see any impact.

Use FK constraints if possible. They are checked before any work is done - meaning - before any data is actually changed.

-Mike

>Hello,
>
>We are in the process of setting up RI (mostly foreign keys, some sp's) on our SQL Server 2000 DBs. One of the questions that has come into play is how bad the performance hit will be once the RI has been put into place. We are using VFP 7 and C# for our front ends, BTW.
>
>I was just wondering if there was anyone out there who has seen any performance difference between an application with RI and one without. If so, how bad of a hit was it, and what type of RI did you use (FKs, SPs, triggers, etc...). If anyone has any advice on how to reduce the performance hit, that would be appreciated as well!
>
>Thanks!
>
>-Justin