Answer Detail: RE: What is difference between UNIQUE and PRIMARY KEY ...

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Question: What is difference between UNIQUE and PRIMARY KEY constraints?

Answer:

A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL.

March 03, 2007 01:23:47	#4
bala	Member Since: Visitor Total Comments: N/A
RE: What is difference between UNIQUE and PRIMARY KEY ...
Primay Key Unique key ----------- ------------------ There is only one there may be more than 1 Primary key for Unique Key in table 1 table It can not contain It Can contain one Null Value Null value

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