- non-equality, and
you have used so far, a row is returned only if a corresponding record in each table is queried.
These types of joins can be categorized as inner joins because records are listed in the results only if a match is found in each table. In fact, the default INNER keyword can be included with the JOIN keyword to specify that only records having a matching row in the corresponding table should be returned in the results.
However, suppose you want a list of all customers (not just ones who have placed an order) and order numbers for orders the customers have recently placed. Recall that the CUSTOMERS table lists all customers who have ever placed an order, but the ORDERS table lists just the current month's orders and unfilled orders from previous months. An inner join might not give you the exact results you want because some customers might not have placed a recent order.
The query shown below produces an equality join that returns all order numbers stored in the ORDERS table and the name of the customer placing the order.