Unique key constraint

Unique key constraint - Part 9

We use UNIQUE constraint to enforce uniqueness of a column i.e the column shouldn't allow any duplicate values. We can add a Unique constraint thru the designer or using a query.
To add a unique constraint using SQL server management studio designer:
1. Right-click on the table and select Design
2. Right-click on the column, and select Indexes/Keys...
3. Click Add
4. For Columns, select the column name you want to be unique.
5. For Type, choose Unique Key.
6. Click Close, Save the table.