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Difference between primary and secondary key?


Date: 05 Jan 2010   Posted By: Vijay Kumar Vishwakarma     Group: Computers    Category: Software   

Can anybody tell me the difference between primary key and secondary key in DBMS, at least 3 points?



Author: Arvind Kumar Chauhan    05 Jan 2010      Member Level: Silver     Points : 4  (Rs 2)    Voting Score: 2

Hi Vijay,

The difference between Primary Key and Secondary Key are stated below:-

Primary Key
1) Is used for Unique Identification of Rows
2) We have only one Primary Key per table
3) A Primary Key is one of the Candidate Keys or you can say one of the irreducible super key, depends on database designer which one he needs.

Secondary Key
1) Is used for Identification of Rows but not usually Unique
2) We can have multiple Secondary Key per table
3) Attribute used for Secondary key are not the ones used for Super Key i.e. Secondary Key is not even be one of the Super Key.

Also if you require more information on DBMS Keys and there examples then please visit the below page
http://www.indiastudychannel.com/resources/101302-DBMS-Keys.aspx

Thanks,
Arvind


Author: Arvind Kumar Chauhan    05 Jan 2010      Member Level: Silver     Points : 4  (Rs 2)    Voting Score: 0

Hi Vijay,

The difference between Primary Key and Secondary Key are stated below:-

Primary Key
1) Is used for Unique Identification of Rows
2) We have only one Primary Key per table
3) A Primary Key is one of the Candidate Keys or you can say one of the irreducible super key, depends on database designer which one he needs.

Secondary Key
1) Is used for Identification of Rows but not usually Unique
2) We can have multiple Secondary Key per table
3) Attribute used for Secondary key are not the ones used for Super Key i.e. Secondary Key is not even be one of the Super Key.

Also if you require more information on DBMS Keys and there examples then please visit the below page
http://www.indiastudychannel.com/resources/101302-DBMS-Keys.aspx

Thanks,
Arvind





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