Difference between primary key and unique key

imain · New User Joined: 25 Jun 2006 Posts: 14 Location: US

Hi All,

Can anybody tell me the exact difference between primary key and unique key.

thanks in advance
imain

guptae · Posted: Mon Aug 14, 2006 2:46 pm

Hi Imain,

For a db2 table primary key can only be 1 but unique key can be more than 1.
Index is created for primary key

neelesht · Posted: Mon Aug 14, 2006 4:08 pm

Hi Imain,

Primary key can never have value NULL but Unique key can have NULL value.

Enjoy....
Neelesh

cheetz007 · New User Joined: 10 Aug 2006 Posts: 23

Isn't it simpler than that? A primary key is the ONLY "real" key to a table - the table is indexed on the primary key. A unique key is any column or combination of columns that MUST have a unique value. The table may or may not be indexed on a unique key... that's up to the DBA and the usage requirements of a table. In effect, a "key" is nothing more than a value (or values) that can be contained within a column.

Clear as mud?