Explanation

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.

A field is also known as a column

that stores the same type of data and hence can be called a category of data.

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vu FIA CBT PAPER 15-12-2021