Unique key by Id

Posted on 2007-03-30
Medium Priority
Last Modified: 2010-03-19
Hi Experts,

Here is my table:
Users (UserId, ApplicationId, UserName...)

I want the username to be unique by ApplicationId when I insert or update.
Can I create a unique key for the username to raise an error on insert or update ? If so, how can I limit the key to check a unique username by ApplicationId and not for  all the table ?

Thanks in advance for your help.
Question by:noulouk
  • 2
LVL 10

Expert Comment

ID: 18826401
You could add a new non-clustered index, including both fields (ApplicationId, UserName) and check the unique box.
LVL 10

Accepted Solution

ksaul earned 2000 total points
ID: 18826447
Or with SQL:

CREATE UNIQUE NONCLUSTERED INDEX [idx_Application_UserName] ON [dbo].[Users]
      [ApplicationId] ASC,
      [UserName] ASC

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