MCQ IN COMPUTER SCIENCE & ENGINEERING

Detailed explanation-1: -A primary key, also called a primary keyword, is a column in a relational database table that’s distinctive for each record. It’s a unique identifier, such as a driver’s license number, telephone number with area code or vehicle identification number (VIN). A relational database must have only one primary key.

Detailed explanation-2: -The primary key is accepted as a unique or sole identifier for every record in the table. In the case of a primary key, we cannot save NULL values. In the case of a unique key, we can save a null value, however, only one NULL value is supported.

Detailed explanation-3: -Primary Key-a field containing a value that uniquely identifies each record in a table. The primary key is unique and prevents entering duplicate records or a null value in that field. Foreign Key-a key in a related table that refers to the primary key in another table.

Detailed explanation-4: -To identify a primary key for a table or file, you locate a column that’s values uniquely identify the rows in the selected table. Additionally, you can verify that a primary key that is defined in the data source is the true primary key.

Detailed explanation-5: -A primary key is a field or set of fields with values that are unique throughout a table. Values of the key can be used to refer to entire records, because each record has a different value for the key. Each table can only have one primary key.