Subqueries

Definition: A subquery is a query nested inside another SQL query, which can be used in SELECT, INSERT, UPDATE, or DELETE statements.

Syntax

SELECT column1 FROM table_name WHERE column2 IN (SELECT column2 FROM another_table);

Example:

SELECT first_name FROM employees WHERE department_id IN (SELECT department_id FROM departments WHERE location_id = 1000);

Explanation: This retrieves names of employees who work in departments located in a specific location_id, using a subquery to find relevant department_ids.