By default, joins are inner joins. This means that rows are included in the result set only if they satisfy the join condition.
For example, each row of the result set of the following query contains the information from one Customers row and one SalesOrders row, satisfying the key join condition. If a particular customer has placed no orders, the condition is not satisfied and the result set does not contain the row corresponding to that customer.
SELECT GivenName, Surname, OrderDate FROM Customers KEY INNER JOIN SalesOrders ORDER BY OrderDate;
Because inner joins and key joins are the defaults, you obtain the same result using the following FROM clause.
FROM Customers JOIN SalesOrders