Question

what is primary key and candidate key?

Answer 1

Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate 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.



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Answer 2

Hey !$<b>$

Primary key: It is a column (or columns) in a table that uniquely identifies each row. A primary key value is  unique and cannot be null. There is only one primary key for a table.

Candidate key: It is a column (or columns) that uniquely identify rows in a table. Any of the identified candidate keys can be used as the table's primary key.