第十一课 使用子查询

11.1 利用子查询进行过滤

子查询从内到外执行，作为子查询的 SELECT 语句只能查询单个列。　　

select cust_name,cust_contact from customers where cust_id in 
(select cust_id from orders where order_num in 
(SELECT order_num FROM OrderItems WHERE prod_id = 'RGAN01'))

 

 子查询经常用于where语句的in中搭配使用