SQL can I have a “conditionally unique” constraint on a table?

Question

I\'ve had this come up a couple times in my career, and none of my local peers seems to be able to answer it. Say I have a table that has a \"Description\" field which is a

Answer 1

If you are using SQL Server 2008 a Index filter would maybe your solution:

http://msdn.microsoft.com/en-us/library/ms188783.aspx

This is how I enforce a Unique Index with multiple NULL values

CREATE UNIQUE INDEX [IDX_Blah] ON [tblBlah] ([MyCol]) WHERE [MyCol] IS NOT NULL