如何在 SQL 中组合多个计数语句

Question

我有一个包含 ID 列表的表格，每个 ID 的状态为 HW、HB、PIP 或 TBC。

我想计算每种状态的人数，所以我会有一个看起来像这样的表格

HW HB PIP 待定

45 27 9 49

我现在有

    (SELECT COUNT(*) AS 'StatusHW' From HomeworkerStatus WHERE Status='Homeworker')
    UNION       
    (SELECT COUNT(*) AS 'StatusHB' From HomeworkerStatus WHERE Status='Home Based')
    UNION
    (SELECT COUNT(*) AS 'StatusPIP' From HomeworkerStatus WHERE Status='PIP') 
    UNION
    (SELECT COUNT(*) AS 'StatusTBC' From HomeworkerStatus WHERE Status='TBC')           

这会返回

状态HW

1 45

2 27

3 9

4 49

我也试过

    SELECT Status,
    sum(case when Status = 'Homeworker' then 1 else 0 end) StatusHW,
    sum(case when Status = 'Home Based' then 1 else 0 end) StatusHB,
    sum(case when Status = 'PIP' then 1 else 0 end) StatusPIP,
    sum(case when Status = 'TBC' then 1 else 0 end) StatusTBC
    FROM HomeworkerStatus
    GROUP BY Status

这将返回一个 4x4 表，其中包含第 1、2、3、4 行和列 Status、StatusHW、...、StatusTBC。这更接近我所追求的，但仍然不对。

任何帮助将不胜感激。

谢谢

Answer 1

只需删除group by，因为在聚合时已经处理了这些条件：

 SELECT 
    -- Status,
    sum(case when Status = 'Homeworker' then 1 else 0 end) StatusHW,
    sum(case when Status = 'Home Based' then 1 else 0 end) StatusHB,
    sum(case when Status = 'PIP' then 1 else 0 end) StatusPIP,
    sum(case when Status = 'TBC' then 1 else 0 end) StatusTBC
    FROM HomeworkerStatus
    -- GROUP BY Status

Answer 2

不要GROUP BY Status，如果你只想要一行：

SELECT
sum(case when Status = 'Homeworker' then 1 else 0 end) StatusHW,
sum(case when Status = 'Home Based' then 1 else 0 end) StatusHB,
sum(case when Status = 'PIP' then 1 else 0 end) StatusPIP,
sum(case when Status = 'TBC' then 1 else 0 end) StatusTBC
FROM HomeworkerStatus;