Primary key is a special field or group of fields in the table that uniquely identifies each record. The primary key does not accept duplicate value and it does not allow blank field or null.
- Advantages of primary key:
- Data can not be repeated. It prevents duplicate records from being entered.
- It makes fast access for database to locate records in the table. Fast sorting and searching records.
- It creates the relationship between tables.
- It avoids null value.