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primary key and unique key
1 Answer(s)      4 years and a month ago
Posted in : JDBC


Whats is mean by primary key and unique key?


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November 12, 2010 at 5:55 PM


Hi friends,

Primary Key:- Primary Key is an attribute or a set of attributes in a table which uniquely identifies a record (row) in a table and no two records (rows) in the table can have the same values for all the columns comprising the primary key.

Unique Key:- A unique key is a key which stores unique values (no duplicates) for that particular column.

Difference between Primary Key & Unique Key:-

  1. A Unique key can store a null value and primary key cannot store any null value.

  2. A primary key can be references to another table as a Foreign Key.

Thanks.



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