重用查詢/子查詢結果以根據列值分配多個輸出

Question

我想根據列的特定狀態分配4個輸出值，同時計算它的出現次數。

例如

   Select @someVariable =(Select count(*) as r
    from table 
    join table 2 as t2
    on r.id= t2.id 
    where getdate() between t2.start and t2.end )

添加額外的where語句，如t2.status="somestatus" ，但是這樣我必須對t2.status="somestatus"不同的狀態進行相同的查詢，是否有可能重用該查詢或以某種方式基於t2.status對輸出變量進行子查詢分配t2.status

為了防止我的代碼示例被搞砸了（只是從內存中寫了一些），我想要做的是，計算有多少列具有特定狀態並適合時間范圍。

我已經完成了我需要的工作，在存儲過程中有多個這樣的查詢，但我不想這樣做。

Answer 1

您可以將查詢編寫為單個select ：

Select @someVariable = count(*)
from table join
     table 2 as t2
     on r.id = t2.id 
where getdate() between t2.start and t2.end;

然后，您可以輕松添加更多變量：

Select @someVariable = count(*),
       @someVariable2 = sum(case when t2.status = 'somestatus' then 1 else 0 end)
from table join
     table 2 as t2
     on r.id = t2.id 
where getdate() between t2.start and t2.end;

Answer 2

你想要這樣的東西嗎？

SELECT 
    @TotalCount = count(*), 
    @Status1 = s1.status1, 
    @Status2 = s2.status2, 
    @Status3 = s3.status3 
FROM [table]
CROSS JOIN (SELECT count(*) as status1 FROM [table] WHERE [status] = 'status1' and getdate() between [start] and [end]) s1
CROSS JOIN (SELECT count(*) as status2 FROM [table] WHERE [status] = 'status2' and getdate() between [start] and [end]) s2
CROSS JOIN (SELECT count(*) as status3 FROM [table] WHERE [status] = 'status3' and getdate() between [start] and [end]) s3

結果將使用一個查詢輸出到變量。