Step-by-step tutorial shows you how to use SQL subqueries in your SELECT statement & FROM and WHERE clauses! Queries: 1) A subquery in the SELECT statement: SELECT customerid, freight, (SELECT AVG(freight) FROM orders) FROM orders 2) A subquery in the FROM clause: SELECT shipcountry, AVG(num_orders) FROM (SELECT customerid, shipcountry, count(*) AS num_orders FROM orders GROUP BY 1,2) sub GROUP BY 1 3) A subquery in the WHERE clause: SELECT * FROM orders WHERE employeeid IN (SELECT employeeid FROM employees WHERE LOWER(firstname) LIKE '%b%') Get the Northwind Database: Support the Channel: 1) Subscribe: 2) DataCamp: 3) Udacity: