What is difference between UNIQUE constraint and PRIMARY KEY constraint ?

A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.

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Thriveni P

  • Mar 14th, 2006
 

A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.

Unique key cannot be used to create referential integrity whereas primary key can do.

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