Question

Difference between primary and Candidate key.
( pointwise answer )

Answer 1

Heya,

PRIMARY KEY:-

(1.) There can be only one primary key in any relation.

(2.) No attribute of a Primary key can contain NULL value.

(3.) It is optional to specify a primary key for any relation.

(4.) Primary key describes the most important attribute for the relation.

(5.) A primary key is a candidate key.
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CANDIDATE KEY:-

(1.) There can be more than one candidate key in a relation.

(2.) The attribute of a Candidate key can have NULL value.

(3.) There can not be a relation without candidate key specified

(4.) Candidate keys present candidates that can qualify for Primary Key.

(5.) It is not compulsory that each candidate key can be a primary key.

HOPE IT HELPS:-))

Answer 2

Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique keyin database.

There can be multipleCandidate Keys in one table. ...
Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record.

Only one Candidate Key can be Primary Key.