Hello everyone Thank you all for your suggestions. I had neither heard of partial unique indexes nor considered using COALESCE so I will explore both of these as options and update the thread with how it goes. >Then, if you can define a problem where you feel having a unique table constraint over >the field is the correct solution [...] you should post the problem and take suggestions on >ways to solve it. I am not sure if I have such a problem :) I tried to simplify my example for the sake of brevity but if I cannot get the above to work I will post the full problem. Kind regards Peter
