118.View the Exhibit and examine the structure of the PROMOTIONS table.

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最新推荐文章于 2016-03-09 17:43:40 发布

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本文通过两个具体的SQL查询案例，分析了WHERE子句与HAVING子句的区别及其对查询结果的影响。指出两者虽然都能实现条件过滤，但作用时机不同，导致最终输出结果存在差异。

118.View the Exhibit and examine the structure of the PROMOTIONS table.
Examine the following two SQL statements:
Statement 1
SQL>SELECT promo_category,SUM(promo_cost) FROM promotions
WHERE promo_end_date-promo_begin_date > 30
GROUP BY promo_category;

Statement 2
SQL>SELECT promo_category,sum(promo_cost) FROM promotions
GROUP BY promo_category
HAVING MIN(promo_end_date-promo_begin_date)>30;
Which statement is true regarding the above two SQL statements?

A.statement 1 gives an error, statement 2 executes successfully
B.statement 2 gives an error, statement 1 executes successfully
C.statement 1 and statement 2 execute successfully and give the same output
D.statement 1 and statement 2 execute successfully and give a different output
答案：D
解析：首先应该确定1和2执行都是正确的，1的条件在where中，是在group by之前进行过滤行
2的条件是在having中，是在group by之后进行过滤的，因此他们不一样