How To Use Subqueries with the IN Operator?

A subquery can be used with the IN operator as "expression IN (subquery)". The subquery should
return a single column with one or more rows to form a list of values to be used by the IN
operation. The following tutorial exercise shows you how to use a subquery with the IN operator:
SQL> SELECT first_name, last_name FROM employees
WHERE department_id IN (
SELECT department_id FROM departments WHERE location_id = 1700
);
FIRST_NAME LAST_NAME
-------------------- -------------------------
Steven King
Neena Kochhar
Lex De Haan
Nancy Greenberg
Daniel Faviet
John Chen
Ismael Sciarra