使用具有不同 JOIN 的同一表的 TSQL 多次计数

Question

我有一个奇怪的情况，不太确定如何处理它。

我有 2 个单独的表：

表A是提交

id
submitterQID
nomineeQID
story

表 B 是员工

QID
Name
Department

我正在尝试获取按部门分组的提交总数以及提名总数。

这就是我的存储过程的样子：

BEGIN
                SELECT   TOP 50 count(A.[nomineeQID]) AS totalNominations,
                                count(A.[subQID]) AS totalSubmissions,
                                B.[DepartmentDesc] AS department
                FROM     empowermentSubmissions AS A
                JOIN empTable AS B
                ON B.[qid] = A.[nomineeQID]
                WHERE A.[statusID] = 3
                AND A.[locationID] = @locale
                GROUP BY B.[Department]
                ORDER BY totalNominations DESC
                FOR      XML PATH ('data'), TYPE, ELEMENTS, ROOT ('root');
            END

这个问题是 JOIN 仅由 nomineeQID 加入，而不是 subQID。

我正在寻找的最终结果是：

部门客户服务有 25 个提交和 90 个提名

按两个计数的总和排序...

我尝试在 subQID 上再次加入 JOIN，但被告知我不能在同一张桌子上加入两次。

有没有更简单的方法来做到这一点？

Answer 1

在这种情况下，您需要彼此独立地收集计数。当两个左连接都满足连接条件时，使用两个左连接将导致某些行在第一个左连接中被计算两次。您可以使用相关子查询或外部应用来解决您的场景，该应用收集不同标准的计数。我没有在这里提供COUNT(CASE ... ) 选项，因为您在数据中没有非此即彼的情况，您有两个外键到employees 表。所以，设置示例数据：

declare @empowermentSubmissions table (submissionID int primary key identity(1,1), submissionDate datetime, nomineeQID INT, submitterQID INT, statusID INT, locationID INT)
declare @empTable table (QID int primary key identity(1,1), AreaDesc varchar(10), DepartmentDesc varchar(20))
declare @locale INT = 0
declare @n int = 1

while @n < 50
begin
    insert into @empTable (AreaDesc, DepartmentDesc) values ('Area ' + cast((@n % 2)+1 as varchar(1)), 'Department ' + cast((@n % 4)+1 as varchar(1)))
    set @n = @n + 1
end
set @n = 1
while @n < 500
begin
    insert into @empowermentSubmissions (submissionDate, nomineeQID, submitterQID, StatusID, locationID) values (dateadd(dd,-(cast(rand()*600 as int)),getdate()), (select top 1 QID from @empTable order by newid()), (select top 1 QID from @empTable order by newid()), 3 + (@n % 2) - (@n % 3), (@n % 2) )
    set @n = @n + 1
end

现在是OUTER APPLY 选项：

SELECT TOP 50 E.DepartmentDesc, SUM(N.Nominations) Nominations, SUM(S.TotalSubmissions) TotalSubmissions
FROM @empTable E
    OUTER APPLY (
        SELECT COUNT(submissionID) Nominations
        FROM @empowermentSubmissions A
        WHERE A.statusID = 3
            AND A.nomineeQID = E.QID
            AND A.locationID = @locale
    ) N
    OUTER APPLY (
        SELECT COUNT(submissionID) TotalSubmissions
        FROM @empowermentSubmissions A
        WHERE A.statusID = 3
            AND A.submitterQID = E.QID
            AND A.locationID = @locale
    ) S
GROUP BY E.DepartmentDesc
ORDER BY SUM(Nominations) + SUM(TotalSubmissions) DESC