Comments on: SQL SERVER – Difference Between Candidate Keys and Primary Key http://blog.sqlauthority.com/2009/05/30/sql-server-difference-between-candidate-keys-and-primary-key/ Personal Notes of Pinal Dave Sun, 12 Feb 2012 09:22:39 +0000 hourly 1 http://wordpress.com/ By: ankita http://blog.sqlauthority.com/2009/05/30/sql-server-difference-between-candidate-keys-and-primary-key/#comment-250050 Wed, 08 Feb 2012 15:38:50 +0000 http://blog.sqlauthority.com/?p=5208#comment-250050 how to identify condidate key plz tell me?

]]> By: anonymous http://blog.sqlauthority.com/2009/05/30/sql-server-difference-between-candidate-keys-and-primary-key/#comment-241288 Fri, 20 Jan 2012 11:59:54 +0000 http://blog.sqlauthority.com/?p=5208#comment-241288 the main reason why it is called “composite key” is because it can only be made of two or more- but not one- attributes. a composite key is not just a primary key: it can be a candidate and superkey as well. but the original meaning lies in the fact that it is made up of more than one attribute

]]> By: Sagar http://blog.sqlauthority.com/2009/05/30/sql-server-difference-between-candidate-keys-and-primary-key/#comment-142463 Mon, 20 Jun 2011 14:21:47 +0000 http://blog.sqlauthority.com/?p=5208#comment-142463 @Jasminder: A composite key is a primary key which has more than 1 column. For example consider the many to many relation between student and courses. Here we need another table , lets say studentcourses .

This studentcourses table will have student id and course id as its columns. This will form your composite key.

Candidate key is a set of columns which can uniquely identify the values in a table and can act as a unique key. One of these candidate keys will become the primary key and the rest will become alternate keys.

Unique key as the name suggests , is used to uniquely identify a value in a table. For example Emp_id etc. Every candidate key will act as a unique key. Unique key can never be a NULL value.

]]> By: Jasminder http://blog.sqlauthority.com/2009/05/30/sql-server-difference-between-candidate-keys-and-primary-key/#comment-62783 Fri, 12 Mar 2010 04:34:15 +0000 http://blog.sqlauthority.com/?p=5208#comment-62783 Can u plz explain what is difference between Composite Key and Candidate Key ?

Also what is importance of Unique Key in Candidate key

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