Thursday, October 13, 2011

Difference between Primary Key and Unique Key

Difference between Primary Key and Unique Key

  • Both Primary Key and Unique Key gives uniqueness of the column on which they are defined.
  • By default Unique Key creates a nonclustered index whereas Primary Key creates a clustered index on the column.
  • A Primary key value cannot be NULL whereas Unique Key allows only one NULL.

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