门| GATE-CS-2016（套装2）|第 62 题

考虑以下名为 water_schemes 的数据库表：

以下 SQL 查询返回的元组数为

with total(name, capacity) as
   select district_name, sum(capacity)
   from water_schemes
   group by district_name
with total_avg(capacity) as
   select avg(capacity)
   from total
select name
   from total, total_avg
   where total.capacity >= total_avg.capacity

(一) 1
(乙) 2
(三) 3
(四) 4答案：(乙)
说明：按区名进行第一组，得到的总容量如下

Ajmer 20
   Bikaner 40
   Charu 30
   Dungargarh 10 

然后计算平均容量，

Average Capacity = (20 + 40 + 30 + 10)/4 
                 = 100/4 
                 = 25.

最后选择超过平均水平的地区。

Bikaner is 40 which is greater than average (25)
Charu is 30 which is also greater than average (25). 

Therefore answer is 2 tuples.

这个问题的测验