Question

4. What do you understand by a primary key​

Answer 1

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.

Explanation:

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Answer 2

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• 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.