How To Use Subqueries with the EXISTS Operator?

A subquery can be used with the EXISTS operator as "EXISTS (subquery)", which returns true if
the subquery returns one or more rows. The following statement is a good example of "EXISTS
(subquery)". It returns rows from employees table that there are rows existing in the departments
table linked to the employees table with location_id = 1700.
SQL> SELECT first_name, last_name FROM employees e
WHERE EXISTS (
SELECT * FROM departments d
WHERE e.department_id = d.department_id AND d.location_id = 1700
);
FIRST_NAME LAST_NAME
-------------------- -------------------------
Steven King
Neena Kochhar
Lex De Haan
Nancy Greenberg
Daniel Faviet
John Chen
Ismael Sciarra