如何为此编写sql查询？

我的桌子看起来像这样：

id  staus
 1    p
 1    p
 1    c
 2    p
 2    c

id  p  c
 1  2  1    <-- id 1 has two rows with 'p' and one row with 'c'
 2  1  1    <-- id 2 has one row with 'p' and one row with 'c'

SELECT
    id
,   SUM (CASE STATUS WHEN 'p' THEN 1 ELSE 0 END) as p
,   SUM (CASE STATUS WHEN 'c' THEN 1 ELSE 0 END) as c
FROM my_table
GROUP BY id

我需要为每个

id

生成状态为

'p'

和

'c'

的行计数，因此我期望的结果如下所示：

id  staus
 1    p
 1    p
 1    c
 2    p
 2    c

id  p  c
 1  2  1    <-- id 1 has two rows with 'p' and one row with 'c'
 2  1  1    <-- id 2 has one row with 'p' and one row with 'c'

SELECT
    id
,   SUM (CASE STATUS WHEN 'p' THEN 1 ELSE 0 END) as p
,   SUM (CASE STATUS WHEN 'c' THEN 1 ELSE 0 END) as c
FROM my_table
GROUP BY id

idpc
1 2你可以这样做：

id  staus
 1    p
 1    p
 1    c
 2    p
 2    c

id  p  c
 1  2  1    <-- id 1 has two rows with 'p' and one row with 'c'
 2  1  1    <-- id 2 has one row with 'p' and one row with 'c'

SELECT
    id
,   SUM (CASE STATUS WHEN 'p' THEN 1 ELSE 0 END) as p
,   SUM (CASE STATUS WHEN 'c' THEN 1 ELSE 0 END) as c
FROM my_table
GROUP BY id

如果要聚合的固定项不止是几个，例如
'p'
和
'c'
，则可能会提供更好的选择。
似乎需要对表进行透视，当我遇到同样的问题时，我使用了一篇简单的文章。从SQLServer2008开始工作

declare @t table(id int, staus char(1))
insert @t values( 1,'p'),( 1,'p'),( 1,'c'),( 2,'p'),( 2,'c')

SELECT id, [p], [c] 
from @t
PIVOT
(count([staus])  
FOR staus
in([p],[c])  
)AS p

结果:

id  p  c
1   2  1
2   1  1

它还有助于提供表定义。