我如何计算这种方式的参与者总数？

Posted 2023-05-08

【中文标题】我如何计算这种方式的参与者总数？

【英文标题】：How do I count the total of number of participants in this way?

【发布时间】：2020-01-31 11:51:52

【问题描述】：

如果我在表格中有这些值：

Description | number of participants | GroupId
------------------------------------------
Alpha          1                       34
Beta           1                       34
Beta           3                       34
Beta           3                       34
Charlie        1                       34
Charlie        2                       34

如何查询才能得到这个结果？

Alpha   11 34
Beta    11 34
Beta    11 34
Beta    11 34
Charlie 11 34
Charlie 11 34

这应该代表相同Id的参与者总数

我正在尝试的 SQL 查询：

SELECT description
    ,COUNT(1) AS Cnt
FROM Table1
GROUP BY description

UNION ALL

SELECT 'SUM' description
    ,COUNT(1)
FROM Table1

【问题讨论】：

mysql 或 SQL Server?

【参考方案1】：

您可以将sum() 与subquery 一起使用：

SELECT description, COUNT(1) as Cnt
FROM Table1
GROUP BY description
UNION ALL
SELECT 'SUM', SUM(Cnt)
FROM (SELECT COUNT(1) AS Cnt
      FROM Table1
      GROUP BY description
     ) C;

但是，在SQL Server 中，您可以使用rollup：

SELECT ISNULL(description, 'SUM') AS description, COUNT(1) as Cnt
FROM Table1
GROUP BY description WITH ROLLUP;'

根据您正在寻找的示例输出 window 函数：

select description, SUM(number_of_participants) OVER (PARTITION BY groupId), groupId
from Table1;

如果窗口功能不支持，您可以使用子查询：

select t.description, 
      (select sum(t1.number_of_participants) 
       from table1 t1 
       where t1.groupid = t.groupid
      ), t.groupid 
from Table1 t;

【参考方案2】：

如果您想要预期输出中提到的所有行的总和，可以使用SUM() over() 窗口函数。

SELECT description,
       SUM(number_of_participants) OVER () as Total,
       groupId 
from your_table.

输出：

+-------------+-------+---------+
| descritpion | total | groupId |
+-------------+-------+---------+
| Alpha       | 11    | 34      |
| Beta        | 11    | 34      |
| Beta        | 11    | 34      |
| Beta        | 11    | 34      |
| Charlie     | 11    | 34      |
| Charlie     | 11    | 34      |
+-------------+-------+---------+

如果您需要每个描述的总和，则使用SUM() OVER (PARTITION BY )

SELECT description,
       SUM(number_of_participants) OVER (partition by description) as Total,
       groupId 
from your_table.

输出：

+-------------+-------+---------+
| descritpion | total | groupId |
+-------------+-------+---------+
| Alpha       | 1     | 34      |
| Beta        | 7     | 34      |
| Beta        | 7     | 34      |
| Beta        | 7     | 34      |
| Charlie     | 3     | 34      |
| Charlie     | 3     | 34      |
+-------------+-------+---------+

【参考方案3】：

在 SQL Server 中，可以使用GROUPING SETS:

SELECT COALESCE(description, 'SUM'), COUNT(1) as Cnt
FROM Table1
GROUP BY GROUPING SETS ( (description), () );