SQL IS NULL Operator

IS NULL operator is used to comparing the NULL value. It is applicable in CRUD operation like create a query, read query, update query, and delete query.

For SELECT Statement

Syntax:-


SELECT column_name(s) 
FROM table_name 
WHERE column_name IS NULL

Example:- Suppose we have employees table which has 7 records


+----+------------+-----------+----------------+-----------+
| id | first_name | last_name | email          | country   |
+----+------------+-----------+----------------+-----------+
|  1 | John       | Tailor    | john@abc.com   | USA       |
|  2 | Rom        | Tailor    | rom@abc.com    | USA       |
|  3 | Andrew     | Symonds   | andrew@abc.com | Australia |
|  4 | Miacle     | Tailor    | miacle@abc.com | Australia |
|  5 | Sachin     | Tendulkar | sachin@abc.com | India     |
|  6 | Virat      | Kohli     | virat@abc.com  | India     |
|  7 | rohit      | NULL      | rohit@abc.com  | India     |

Find the employees details that have last_name value is NULL

Query:-


SELECT * FROM employees WHERE last_name IS NULL;

Output:-


+----+------------+-----------+---------------+---------+
| id | first_name | last_name | email         | country |
+----+------------+-----------+---------------+---------+
|  7 | rohit      | NULL      | rohit@abc.com | India   |
+----+------------+-----------+---------------+---------+
1 row in set (0.00 sec)

SQL IS NULL Operator – Interview Questions

Q 1: What is IS NULL used for?

Ans: It checks for NULL values.

Q 2: Can = be used for NULL comparison?

Ans: No.

Q 3: Is NULL equal to zero?

Ans: No.

Q 4: Can IS NULL be indexed?

Ans: Yes, in many databases.

Q 5: Can IS NULL be used in WHERE?

Ans: Yes.