what is the difference between unique and primary key

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what is the difference between unique and primary key

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Re: what is the difference between unique and primary key

Answer
# 1

Primary key is the combination of unique and not null.But 
unique key accepts null values also.

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Ravi Kanth

Re: what is the difference between unique and primary key

Answer
# 2

Unique Key allows NULL value and a table can have more than 
one UNIQUE KEY Constraint.

Primary Key is the combination of UNIQUE+NOT NULL,means it 
won't allow NULL Values and a table can have only one 
Primary Key.But a table can have Composite Primary Key.

Thank you,
Suresh

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Suresh Kumar Somayajula

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