What's the difference between a primary key and a unique key?

 Posted by Majith on 7/21/2008 | Category: Sql Server Interview questions | Views: 10685

Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only.

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Posted by: Vivekjj on: 10/5/2012 | Points: 10
primary key and unique key does not allow repeated values but one difference is primary key not allow null values but unique key allows null values

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