Lesson 18 / 30
Subqueries
Nest queries as subqueries, including scalar and correlated forms, to filter or compute from other results.
Subquery in WHERE
A subquery runs first and feeds its result into the outer query.
SELECT name FROM customers
WHERE id IN (
SELECT customer_id FROM orders WHERE amount > 1500
);Output:
name Asha Rao
Scalar & correlated subqueries
A scalar subquery returns a single value; a correlated subquery references the outer query's row and re-runs for each one.