Is null operator

COMPARE NULL IN SQL

If you want to find out if a column contains any null values, then you can use the is NULL operator in the where clause.

A null value means that the value is unavailable. You cannot test for null values using an equal sign, because a Null value cannot be equal for unequal any value.

For example you want to retrieve the names of employees who do not have a manager . you can use the IS NULL operator to find all rows that contain a null value in the MGR column.

SQL> select ename

    from emp

    where mgr is null;

     ENAME

    ----------

     KING