Question 21Differentiate between primary key and candidate key in a relation.

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Primary keyCandidate keyA primary key is a set of one or more attributes/fields which uniquely identifies a tuple/row in a table.A candidate key refers to all the attributes in a relation that are candidates or are capable of becoming a primary key.There can be only one primary key per table.A table can have multiple candidate keys. Only one of them is chosen as the primary key.

Primary key	Candidate key
A primary key is a set of one or more attributes/fields which uniquely identifies a tuple/row in a table.	A candidate key refers to all the attributes in a relation that are candidates or are capable of becoming a primary key.
There can be only one primary key per table.	A table can have multiple candidate keys. Only one of them is chosen as the primary key.

Structured Query Language (SQL) — Question 27

Question 21