An inner join only returns rows where there is a match in both tables. For example, if you have a table with customer information and another table with purchase history, an inner join will only return customers who have made a purchase.
Here is a basic SQL example: sql SELECT customers.email, purchases.product_name FROM customers INNER JOIN purchases ON customers.customer_id = purchases.customer_id;
This query combines the `customers` table with the `purchases` table based on a common column, `customer_id`.