difference between Primary key and Unique Key

Primary key	Unique Key
1- Primary key doesn’t have null value. 2- A table can have only one primary key. 3- By default primary key have clustered index.	Unique key can hold null value but only once. A table can have more than on unique key. By default Unique key have non- clustered index.

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Bulk Update in sql server 2008..

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SQL Server queries

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