diff between primary key and unique index

rajesh822 · New User Joined: 22 Sep 2005 Posts: 5

what is diff between primary key and unique index?

Rajesh

ikumar · Active User Joined: 02 Aug 2005 Posts: 86

Primary Key: a relational database constraint. Primary key consists of one or more columns that uniquely identify a row in the table. For a normalized relation, there is one designated primary key.

Unique index: a physical object that stores only unique values. There can be one or more unique indexes on a table.

harinatha · New User Joined: 24 Jul 2005 Posts: 31

Hi,

Here one more point is added.

Unique key can have one null value(only one), but not in Primary key.

Thanks & Regards,
Hari.

khamarutheen

hi frnd,
the primary key is a key which holds only the unique value and the primary key is set active if the unique index is created where the physical storage is created for the unique values.

Kavitha Palani · New User Joined: 16 Nov 2005 Posts: 9

Primary Key: a relational database constraint. Primary key consists of one or more columns that uniquely identify a row in the table. For a normalized relation, there is one designated primary key.
Unique index: a physical object that stores only unique values. There can be one or more unique indexes on a table.