Multiple choice

Which of the following is not true for a primary key in DBMS?

  1. It uniquely identifies a row in a table.

  2. Its attributes cannot be duplicated in a row.

  3. It cannot be null.

  4. It is mandatory to provide input for the primary key attributes.

  5. It can be a composite key.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Primary key is chosen by a designer to uniquely identify rows in the table. It is always not null and unique. A null value can be used to represent an unknown data.

Keep practicing — related questions