How to Create Unique Constraints in SQL Server 2005?

Adding Unique Constraints in SQL Server 2005

This guide demonstrates how to enforce uniqueness on columns within an existing SQL Server 2005 table. We'll cover both Transact-SQL (T-SQL) and the graphical Database Diagram methods.

Method 1: Using T-SQL

Employ the following T-SQL statement to add a unique constraint:

<code class="language-sql">ALTER TABLE YourTableName ADD CONSTRAINT YourConstraintName UNIQUE NONCLUSTERED (YourColumnName)</code>

Remember to replace:

• YourTableName with your table's name.
• YourConstraintName with a descriptive name for the constraint.
• YourColumnName with the column you wish to make unique.

Method 2: Utilizing the Database Diagram

1. Right-click your table in the Database Diagram and choose "Indexes/Keys".
2. Click "Add" to create a new index.
3. In the Properties window, select the column(s) to be unique using the ellipsis button.
4. Set the "Is Unique" property to "Yes".
5. Provide a suitable name for the constraint.

These methods ensure data integrity by preventing duplicate entries in the specified column(s). Choose the approach that best suits your workflow.

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