MCQ IN COMPUTER SCIENCE & ENGINEERING

Detailed explanation-1: -A primary key column cannot have NULL values. A table can have only one primary key, which may consist of single or multiple fields.

Detailed explanation-2: -Primary key constraints NULL values are not allowed. If the column(s) contain NULL values, the system will not add the primary key constraint. See ALTER TABLE statement for more information. A table can have at most one PRIMARY KEY constraint.

Detailed explanation-3: -The given statement is true. A primary key pinpoints individual entry in the table. It’s a handy key for locating the record in the table in a distinguishing fashion. The value in a primary key is different and cannot match with any other record in the table. The table’s primary key serves as its unique identification.

Detailed explanation-4: -The statement that is false regarding primary key is: Only parent tables must have a primary key. Because, a primary key must be unique, it can be made up of multiple attributes and it must not contain a null value.

Detailed explanation-5: -Each table can only have one primary key. Access can automatically create a primary key field for you when you create a table, or you can specify the fields that you want to use as the primary key. This article explains how and why to use primary keys. To set a table’s primary key, open the table in Design view.