Create a constraint or rule?

[sqlval]

I need to put a constraint or rule on the column: if it's not null, it should be unique. I am not good with constraints at all. Can they be conditional? Your help is appreciated.

 

[markros]

In SQL Server 2008 you can use UNIQUE filtered INDEX.
Otherwise I believe there was a thread in MSDN in Database Design forum on this exact topic, I'll try to find it.

PluralSight Learning Library

 

[markros]

Found this thread by Google search - it's slightly different problem, but the same idea should apply

http://social.msdn.microsoft.com/Fo...n/thread/a0c73442-8f2c-4068-a5eb-2408ad16d60b

PluralSight Learning Library

 

[sqlval]

Thank you for the link.