What's 'error: subquery returns more than 1 row' in sql?

This error suggests that a subquery used in an SQL statement is returning multiple rows when only one row was expected.

Example:

SELECT * FROM orders WHERE customer_id = (SELECT id FROM customers WHERE name LIKE '%A%');

Solution:

SELECT * FROM orders WHERE customer_id IN (SELECT id FROM customers WHERE name LIKE '%A%');

Use the 'IN' keyword instead of '=' when expecting multiple rows from a subquery.