题目介绍: 活动参与者 activity-participants
难度中等
SQL架构
表:
Friends
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| name | varchar |
| activity | varchar |
+---------------+---------+
id 是朋友的 id 和该表的主键
name 是朋友的名字
activity 是朋友参加的活动的名字
表:
Activities
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| name | varchar |
+---------------+---------+
id 是该表的主键
name 是活动的名字
写一条 SQL 查询那些既没有最多,也没有最少参与者的活动的名字
可以以任何顺序返回结果,Activities 表的每项活动的参与者都来自 Friends 表
下面是查询结果格式的例子:
``` Friends 表: +------+--------------+---------------+ | id | name | activity | +------+--------------+---------------+ | 1 | Jonathan D. | Eating | | 2 | Jade W. | Singing | | 3 | Victor J. | Singing | | 4 | Elvis Q. | Eating | | 5 | Daniel A. | Eating | | 6 | Bob B. | Horse Riding | +------+--------------+---------------+
Activities 表: +------+--------------+ | id | name | +------+--------------+ | 1 | Eating | | 2 | Singing | | 3 | Horse Riding | +------+--------------+
Result 表: +--------------+ | activity | +--------------+ | Singing | +--------------+
Eating 活动有三个人参加, 是最多人参加的活动 (Jonathan D. , Elvis Q. and Daniel A.) Horse Riding 活动有一个人参加, 是最少人参加的活动 (Bob B.) Singing 活动有两个人参加 (Victor J. and Jade W.) ```
sql
select activity
from (
select activity,
rank()over(order by cnt) rk1,
rank()over(order by cnt desc) rk2
from
(
select activity ,count(*) cnt
from Friends
group by activity
)t1
)t2
where rk1 !=1 and rk2 != 1
不需要关联 Activities表,因为 至少有一人参加