Question

DEFINE PRIMARY KEY ?​

Answer 1

Explanation:

The primary key is a field which uniquely identifies each record in a table in a relational database: It can be pre-existing data, for example National Insurance Number. It can be generated specifically for use in the database, eg admission number for a school student.

Answer 2

Answer:

In the relational model of databases, a primary key is a specific choice of a minimal set of attributes that uniquely specify a tuple in a relation. Informally, a primary key is "which attributes identify a record", and in simple cases are simply a single attribute: a unique id.

Explanation:

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