【2019年8月】OCP 071认证考试最新版本的考试原题-第18题

Choose two

Which two statements are true about the WHERE and HAVING clouses in a SELECT statement?

A) The WHERE clause can be used to exclude rows after divding them into groups

B) WHERE and HAVING clauses can be used In the same statement only if applied to dfferent table columns.

C) The HAVING clause can be used with aggregating functions in subqueries.

D) Aggregating functions and columns used in HAVING clauses must be spectfied in thes SELECT list of a query.

E) The WHERE clause can be used to exclude rows before dviding them into goups.

Answer：CE

(解析：having 子句是可以跟子查询进行配合使用，而且子查询中也可以有分组函数;

Oracle 先过滤再分组，照样子可以减少数据的处理数量;

D 档案说在 having 子句中用到列必须出现在 select 子句中，这是不需要的。)