Question

what is a primary key​

Answer 1

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

Answer 2

☆ Answer ☆

One field of the table is created to store unique values. Each such unique value identifies the record uniquely. Such field is called primary key field. Primary key uniquely identifies each record in a table.

Properties of Primary Key :-

• It should always store some value. No null values are allowed in primary key field.

• It should store unique value.

• Once decided, the value must not change as long as that record remain in the database.

Table containing a primary key is also called parent table.