在相关子查询中使用 WHERE 时出错答案

【问题标题】：Error when using WHERE in Correlated Subquery在相关子查询中使用 WHERE 时出错
【发布时间】：2015-03-05 18:09:23
【问题描述】：

我有以下关系：银行 -> 融资 -> 合同 -> 供应商

我必须使用以下查询选择与供应商相关的所有银行：

SELECT DISTINCT A.Name AS BankName, A2.Name as SupplierName
FROM Companies A
INNER JOIN Financing F ON F.IdFinancialCompany = A.Id
INNER JOIN Contracts C ON F.IdContract = C.Id
INNER JOIN Companies A2 ON C.IdSupplier = A2.Id
GROUP BY A.Name, A2.Name

到目前为止，一切都很好。

现在我必须列出有效的合同数量和总合同数量，所以我考虑包含一个子查询：

SELECT DISTINCT A.Name AS BankName, A2.Name as SupplierName,
(SELECT COUNT(C.Id)),
(SELECT COUNT(C.Id) WHERE C.ContractStatus = 1)
FROM Companies A
INNER JOIN Financing F ON F.IdFinancialCompany = A.Id
INNER JOIN Contracts C ON F.IdContract = C.Id
INNER JOIN Companies A2 ON C.IdSupplier = A2.Id 
GROUP BY A.Name, A2.Name

第 2 行运行良好，但在第 3 行出现错误：

选择列表中的“Contracts.ContractStatus”列无效，因为它既不包含在聚合函数中，也不包含在 GROUP BY 子句中。

我希望得到以下结果：

银行名称 |供应商名称 |总合同 |有效合同

银行 1 |供应商 1| 5 | 2

我怎样才能做到这一点？我正在使用 SQL Server 2014

提前致谢！

【问题讨论】：

SUM(case C.ContractStatus when 1 then 1 end)

标签： sql-server subquery where-clause correlated-subquery

【解决方案1】：

从你的 group by 中删除 distinct 并使用 CASE

SELECT A.Name AS BankName, A2.Name as SupplierName,
COUNT(C.Id),
SUM(CASE WHEN C.ContractStatus = 1 THEN 1 ELSE 0 END) 
FROM Companies A
INNER JOIN Financing F ON F.IdFinancialCompany = A.Id
INNER JOIN Contracts C ON F.IdContract = C.Id
INNER JOIN Companies A2 ON C.IdSupplier = A2.Id 
GROUP BY A.Name, A2.Name

【讨论】：