OCP-1Z0-051-V9.02-154题

154. View the Exhibit and evaluate structures of the SALES, PRODUCTS, and COSTS tables.

Evaluate the following SQL statement:

SQL>SELECT prod_id FROM products

INTERSECT

SELECT prod_id FROM sales

MINUS

SELECT prod_id FROM costs;

Which statement is true regarding the above compound query?

A. It produces an error.

B. It shows products that were sold  and have a cost recorded.

C. It shows products that were sold  but have  no cost recorded.

D. It shows products that  have a cost recorded irrespective of sales.

Answer: C

答案解析：

按照题意，查询出在sales表里的已经卖出去的但是不在costs表里的产品id。

 

INTERSECT Example The following statement combines the results with the INTERSECT operator, which returns only those unique rows returned by both queries

返回共同有的唯一的行

MINUS Example The following statement combines results with the MINUS operator, which returns only unique rows returned by the first query but not by the second

返回第一个有，第二个表无的行

官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e41084/queries004.htm#i2054381