Nested Subqueries

A nested subquery is a subquery inside another subquery.

Source data — Pattern 8: Subqueries

All queries run against the shared employees and departments tables (see schema.sql). This pattern introduces scalar, correlated, and multiple-row subqueries. Topics 47 and 48 demonstrate the EXISTS and NOT EXISTS operators, while Topics 49 and 50 introduce the ANY (SOME) and ALL comparison operators.

Nested Subqueries — source table 1

Nested Subqueries — source table 2

What it does

A nested subquery is a subquery inside another subquery. It is commonly used to solve complex problems such as finding the second highest salary.

Problem

Find the second highest salary using subqueries.

SELECT MAX(salary)
FROM employees
WHERE salary < (
SELECT MAX(salary)
FROM employees
);

Result

Nested Subqueries — result 1

SQL · Pattern 8 — Subqueries