Oracle Error PLS-00319: subquery in an IN or NOT IN clause must contain exactly one column

Oracle Error Message

PLS-00319: subquery in an IN or NOT IN clause must contain exactly one column

Reason for the Error

An invalid expression such as X IN (SELECT A,B …) was used. When a [NOT]IN clause is used with a subquery, it does not test for set membership. The number of expressions in the [NOT]IN clause and the subquery select list must match. So, in the example above, the subquery must specify at most one column.

Solution

Change the subquery to select only one column.