INNER JOIN | Learn SQL

INNER JOIN Connects Matching Rows

INNER JOIN connects rows from two tables only when the values in a chosen column match. Matching customers.id with orders.customer_id combines customer and order information into one row. If no matching row exists, that row does not remain in the result.

GOAL

Predict which rows remain after an INNER JOIN.

Does a customer without an order remain in an INNER JOIN of customers and orders?

CHECK IT

SELECT c.name, o.id, o.status
FROM customers c
JOIN orders o ON c.id = o.customer_id

Join key / paired rowsabcNo partner (not in the result)

customers6 rows

id	name
1	Alice
2	Bob
3	Carol
4	Dave
5	Erin
6	Frank

orders8 rows

id	customer_id	status
1	1	shipped
2	1	paid
3	2	shipped
4	3	cancelled
5	3	shipped
6	4	paid
7	5	shipped
8	1	paid

A join combines two tables into one. customers and orders each have a column that points to the same customer.