Oracle Database Interview Question:

How To Use Subqueries with the EXISTS Operator in Oracle?

Submitted by: Administrator

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
2 WHERE EXISTS (
3 SELECT * FROM departments d
4 WHERE e.department_id = d.department_id
5 AND d.location_id = 1700
6 );
<pre>FIRST_NAME LAST_NAME
-------------------- -------------------------
Steven King
Neena Kochhar
Lex De Haan
Nancy Greenberg
Daniel Faviet
John Chen
Ismael Sciarra
......</pre>
Submitted by: Administrator