Difference between primary key and candidate …

<th>Primary Key</th> <th>Candidate Key</th> <th>Primary key is a minimal super key. So there is one and only one primary key in a relation.</th> <th>While in a relation there can be more than one candidate key.</th> <th>Any attribute of Primary key can not contain NULL value.</th> <th>While in Candidate key any attribute can contain NULL value.</th> <th>Primary key can be optional to specify any relation.</th> <th>But without candidate key there can’t be specified any relation.</th> <th>Primary key specifies the important attribute for the relation.</th> <th>Candidate specifies the key which can qualify for primary key.</th> <th>Its confirmed that a primary key is a candidate key.</th> <th>But Its not confirmed that a candidate key can be a primary key.</th>

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