Question of the Day Four

Let us continue our question of the day series with day four.

What is the difference between a primary key and a unique key?

The unique key and the primary key designation both enforce that the particular column is unique.  However, the primary key will create a clustered index using that column and a unique key will create a non-clustered index.  This is the fundamental difference in the two.  Another minor difference is that the unique key allows you to have one null value and the primary key does not allow any use of the null value.



About SQLGator

Microsoft Data Platform MVP, Florida Gator, Star Wars fanatic and is there anything else...oh yeah PS4! I am a geek and SQL Server Business Intelligence Consultant, there are other technologies greater than these? Not so fast my friend! I also love to travel to new and exotic places.

Posted on August 6, 2012, in SQL Schoolhouse and tagged . Bookmark the permalink. Leave a comment.

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