Many common joins are between two tables related by a key. The most common join restricts foreign key values in one table to be equal to primary key values in another table. The example you have already seen restricts foreign key values in the SalesOrders table to be equal to the candidate key values in the Employees table.
SELECT Surname, EmployeeID, OrderDate FROM SalesOrders, Employees WHERE SalesOrders.SalesRepresentative = Employees.EmployeeID
The query can be more simply expressed using a KEY JOIN, as described in the following section.
