Define the Primary key and its Importance.

The key or field that is used to uniquely identify records from the database table is called the primary key. It must be unique and cannot be kept empty(null). The importance of the primary key are :

• It uniquely identifies records.
• It helps in faster access to data.
• It helps to prevent duplication of data.
• It avoids empty(null) values.
• It is used to establish table relationships.