OCP-1Z0-051-V9.02-140题

140. Examine the structure of the PRODUCTS table:

name          Null        Type

PROD_ID       NOT NULL    NUMBER(4)

PROD_NAME                VARCHAR2(20)

PROD_STATUS              VARCHAR2(6)

QTY_IN_HAND              NUMBER(8,2)

UNIT_PRICE               NUMBER(10,2)

You want to display the names of the products that have the highest total value for UNIT_PRICE *

QTY_IN_HAND.

Which SQL statement gives the required output?

A. SELECT prod_name 

FROM products 

WHERE (unit_price * qty_in_hand) = (SELECT MAX(unit_price * qty_in_hand) 

FROM products);

B. SELECT prod_name 

FROM products 

WHERE (unit_price * qty_in_hand) = (SELECT MAX(unit_price * qty_in_hand) 

FROM products 

GROUP BY prod_name);

C. SELECT prod_name 

FROM products 

GROUP BY prod_name 

HAVING MAX(unit_price * qty_in_hand) = (SELECT MAX(unit_price * qty_in_hand) 

FROM products 

GROUP BY prod_name);

D. SELECT prod_name 

FROM products 

WHERE (unit_price * qty_in_hand) = (SELECT MAX(SUM(unit_price * qty_in_hand)) 

FROM products) 

GROUP BY prod_name;

Answer: A

答案解析：

BC都犯了一个错误，都会返回一个错误single-row subquery returns more than one row。

即是单行子查询返回了多行。该WHERE子句包含一个等于(=) 运算符，该运算符是一个只需要一个值的单行比较运算符。=运算符无法接受子查询中的多个值，因此产生了错误。

D的查询条件不满足题意。