OCP-1Z0-051 第129题 RIGHT OUTER JOIN的使用

一、原题

View the Exhibits and examine the structures of the PROMOTIONS and SALES tables.



Evaluate the following SQL statement:

SQL>SELECT p.promo_id, p.promo_name, s.prod_id

FROM sales s RIGHT OUTER JOIN promotions p

ON (s.promo_id = p.promo_id);

Which statement is true regarding the output of the above query?

A. It gives the details of promos for which there have been sales.

B. It gives the details of promos for which there have been no sales.
C. It gives details of all promos irrespective of whether they have resulted in a sale or not.
D. It gives details of product ID s that have been sold irrespective of whether they had a promo or not.

答案：C

二、题目翻译

查看PROMOTIONS and SALES表的结构

评估下面的SQL语句

关于上面查询的输出哪句话是正确的？

A.输出已经销售的promos。

B.输出没有销售的promos。

C.不管有没有销售，输出所有的promos。

D.不管有没有promos，输出所有产品ID。

三、题目解析

因为使用的是RIGHT OUTER JOIN，所以会以右表promotions为准，输出所有的促销信息,不管有没有销售，没有的话，显示为空。

表连接的用法，详见：

        http://blog.csdn.net/holly2008/article/details/25704471