MCQ IN COMPUTER SCIENCE & ENGINEERING

Detailed explanation-1: -A primary key consists of one or more fields that uniquely identify each record that you store in the table. Often, there is a unique identification number, such as an ID number, a serial number, or a code, that serves as a 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: -Primary Key(non-null key) is a column of the table that identifies every record that should be unique in the table. The primary Key column should not contain any duplicate values(every column value in the primary key column should be unique), therefore there should only be one primary key column in the table.

Detailed explanation-5: -Often, a unique identification number, such as an ID number or a serial number or code, serves as a primary key in a table. For example, you might have a Customers table where each customer has a unique customer ID number. The customer ID field is the primary key.