SQL SERVER – Create Unique Constraint on Table Column on Existing Table

by using UNIQUE for Unique constraint.

Syntax:

   UNIQUE([col name])

Example:

USE tempdb
GO
-- Create Table
CREATE TABLE Table1 (ID INT, Col1 VARCHAR(100))
GO
-- Alter Table Create Constraint
ALTER TABLE Table1
ADD CONSTRAINT UX_Constraint UNIQUE (Col1)
GO
-- Clean up
DROP TABLE Table1
GO