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A primary key is a special relational database table column (or combination of columns) designated to uniquely identify all table records. A primary key's main features are: It must contain a unique value for each row of data. It cannot contain null values.



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.

What is Primary Key ?

  • A primary key, also called a primary keyword, is a key in a relational database that is unique for each record.

  • It is a unique identifier, such as a driver license number, telephone number (including area code), or vehicle identification number (VIN).

  • A relational database must always have one and only one primary key.

  • For example, in the table CustomerNo, which displays the ID number assigned to different customers, is the primary key. CUSTOMERS.

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