Question

3.
Explain the use of Primary key in a table.
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Answer 1

Answer:

The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

Answer 2

Answer:

A primary key is a field in a table which uniquely identifies each row/record in a database table. When multiple fields are used as a primary key, they are called a composite key. If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s).

Explanation: