创建高级联结

使用表别名

SELECT cust_name, cust-contact
FROM Customers AS C, Orders AS O, OrderItem AS OI
WHERE C.cust_id = O.cust_id
AND OI.prder_num = O.order_num
AND prod_id = 'RGAN01';

自联结

SELECT c1.cust_id, c1.cust_name, c1.cust_contact
FROM Customers AS c1, Customers AS c2
WHERE c1.cust_name = c2.cust_name
AND c2.cust_cantact = 'Jim Jones';

外连结

SELECT Customers_cust_id, Orders.orders_num
FROM Customers LEFT OUTER JOIN Orders
ON Customers.cust_id = Orders.cust_id;