OCP-1Z0-051 第118题 GROUP BY,HAVING子句

一、原题

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

二、题目翻译

查看PROMOTIONS表的结构
评估下面的2个语句
关于上面两个SQL语句，哪句话是正确的？
A.语句1报错，语句2执行成功。
B.语句2报错，语句1执行成功。
C.都执行成功，并给出相同结果。
D.都执行成功，但给出不同的结果。

三、题目解析
      WHERE是分组之前筛选数据，HAVING是分组之后筛选数据，所以结果是不一样的。