SQL 更改查询以返回所有用户的结果

Question

我使用 sql server 并且我有表格：

tbl_GroupUser:
user_id, group_id

这是一个包含用户及其所在组的表（每个组有多个 user_id，每个用户有多个组）。

tbl_group:
id, name

tbl_User:
id, age,....(information about the user)

tbl_Group 的 id 与 group_id 以及 tbl_User 的 id 与 user_id 之间存在一对多的关系。

我创建了一个查询，该查询返回特定用户的组中只有 2 个用户的百分比，并且我想要一个返回所有用户结果的查询。这是我提出的查询：

SELECT cast((SELECT count(*) FROM 
(SELECT user_id FROM tbl_GroupUser WHERE group_id in 
(SELECT group_id FROM (SELECT t1.group_id, count(distinct t1.user_id) as numberOfUsers 
FROM tbl_GroupUser as t1 JOIN tbl_GroupUser as t2 ON t1.group_id = t2.group_id group by
t1.group_id) y WHERE y.numberOfUsers = 2)) as x WHERE x.user_id = 'user') as decimal) * 100 /
(SELECT count(*) FROM tbl_GroupUser WHERE user_id = 'user')

这意味着，计算用户所在的包含 2 个用户的所有组，然后除以用户所在的组总数。

我想要的一个例子：

tbl_GroupUser：

group_id | user_id
------------------
 1       | 1
 1       | 2
 2       | 1

结果：

user_id | p_Grp2
----------------
 1      | 50.0
 2      | 100.0

Answer 1

简单的创建用户定义函数并在选择查询中使用

  alter function UDF_GetPercentage(@UserId int)
returns decimal(18,10)
as begin 

declare @Percentage decimal(18,10)
SELECT @Percentage = cast(
(SELECT count(*) FROM 
(SELECT user_id FROM tbl_GroupUser WHERE group_id in 
(SELECT group_id FROM (SELECT t1.group_id, count(distinct t1.user_id) as numberOfUsers 
FROM tbl_GroupUser as t1 JOIN tbl_GroupUser as t2 ON t1.group_id = t2.group_id group by
t1.group_id) y 
WHERE y.numberOfUsers = 2)
)
as x

WHERE x.user_id in (@UserId)
) as decimal)
* 100 
/
(SELECT count(*) FROM tbl_GroupUser WHERE user_id in (@UserId ))

return @Percentage

end

并在这样的选择查询中使用

SELECT   user_id, dbo.UDF_GetPercentage(user_id) as p_Grp2
FROM     tbl_GroupUser
group by user_id

Answer 2

你不是在尝试这么简单的事情吗？

SELECT user_id, 100.0/COUNT(0) as p_Grp
FROM tbl_User u
INNER JOIN tbl_GroupUser gu ON gu.userId = u.Id
GROUP BY user_id;

Answer 3

使用窗口函数即时统计组成员，然后汇总每个用户的数据：

select user_id, 100.0 * count(case when cnt = 2 then 1 end) / count(*)
from
(
  select 
    user_id,
    count(*) over (partition by group_id) as cnt -- cnt = 2 marks a "two" group
  from tbl_groupuser
)
group by user_id
having count(case when cnt = 2 then 1 end) > 0; -- user in at least one "two" group