OCP-1Z0-051-2015-37题

See the exhibit and examine the structure of the CUSTOMERS and GRADES tables:



You need to display names and grades of customers who have the highest credit limit.

Which two SQL statements would accomplish the task? (Choose two.)

A.

SELECT custname, grade

FROM customers, grades

WHERE (SELECT MAX(cust_credit_limit)

FROM customers) BETWEEN startval and endval;

B.

SELECT custname, grade

FROM customers, grades

WHERE (SELECT MAX(cust_credit_limit)

FROM customers) BETWEEN startval and endval

AND cust_credit_limit BETWEEN startval AND endval;

C.

SELECT custname, grade

FROM customers, grades

WHERE cust_credit_limit = (SELECT MAX(cust_credit_limit)

FROM customers)

AND cust_credit_limit BETWEEN startval AND endval;

D.

SELECT custname, grade

FROM customers , grades

WHERE cust_credit_limit IN (SELECT MAX(cust_credit_limit)

FROM customers)

AND MAX(cust_credit_limit) BETWEEN startval AND endval;

Answer: B,C

Explanation:题意要求显示有最高credit limit的用户的名称和等级，但是须在startval endval 之间。

A，缺少cust_credit_limit BETWEEN startval AND endval这个条件。
BC，使用的非等值连接
B选项，第一个条件(SELECTMAX(cust_credit_limit) FROM
customers) BETWEEN startval and endval
确定最大值所在的级别，但第二个条件cust_credit_limit BETWEEN startval AND endval;会把比最大值小，但
同属一个级别的顾客检索出来。

D语法错误，后一个条件里的分组函数不应出现（此处应该用子查询）