SQL Server 2005 How Create a Unique Constraint?

Question

How do I create a unique constraint on an existing table in SQL Server 2005?

I am looking for both the TSQL and how to do it in the Database Diagram.

Answer 1

The SQL command is:

ALTER TABLE <tablename> ADD CONSTRAINT
            <constraintname> UNIQUE NONCLUSTERED
    (
                <columnname>
    )

See the full syntax here.

If you want to do it from a Database Diagram:

• right-click on the table and select 'Indexes/Keys'
• click the Add button to add a new index
• enter the necessary info in the Properties on the right hand side:
  • the columns you want (click the ellipsis button to select)
  • set Is Unique to Yes
  • give it an appropriate name