How can I create a SQL unique constraint based on 2 columns?

Question

I have a Table like this one:

|UserId   |  ContactID |  ContactName 
---------------------------------------
| 12456   |  Ax759     |  Joe Smith
| 12456   |          


        

Answer 1

You can try this:

CREATE UNIQUE CLUSTERED INDEX index_name ON TABLE (col1,col2)
or
CREATE UNIQUE NONCLUSTERED INDEX index_name ON TABLE (col1,col2)

or

ALTER TABLE [dbo].[TABLE] ADD CONSTRAINT
UNIQUE_Table UNIQUE CLUSTERED
(
col1,
col2
) ON [PRIMARY]