如何在 SQL Server 中连接 3 个表并根据 2 个关键字段计算值

Question

我有 3 个表需要连接，其中 2 个对于计算值并在第三个表中提供它很重要，问题是在这 2 个表中我有 2 个字段需要分组以进行计算。这些是表格：

第一张表：

SELECT    customerId, baseCurrencyId, SUM(amount) AS totalRecovered
FROM      dbo.RecoveredDebt
WHERE     (isDeleted = 0)
GROUP BY  customerId, baseCurrencyId;

首次查询结果：

客户ID	基础货币ID	已恢复总数
2	1	950
4	1	10
1	2	100
2	2	500

第二张表：

SELECT    customerId, baseCurrencyId, SUM(amount) AS totalOld
FROM      dbo.OldDebt
WHERE     (isDeleted = 0)
GROUP BY  customerId, baseCurrencyId;

第二次查询结果：

客户ID	基础货币ID	总旧
2	1	2000
1	2	100
2	2	300

现在技巧来了，我想从客户表中进行选择并具有以下字段： id（客户 ID）、baseCurrencyId、totalOldDebt（来自第一个查询）、totalRecoveredDebt（来自第二个查询）、totalDebt（totalOldDebt -totalRecoveredDebt）。但我希望它按 baseCurrencyId 进行分组，例如，如果客户有超过一种货币的债务，则必须对每个货币进行计算，如果一个表中存在包含一种货币的行，但另一个表中没有，则这些值因为那一定是 zore 并且计算仍然会发生。

这是我根据提供的表格计算后的预期结果：

id	基础货币ID	旧债总额	已收回债务总额	债务总额
1	2	100	100	0
2	1	2000	950	1050
2	2	300	500	-200
4	1	0	10	-10

我尝试过使用 CTE，但我不知道该怎么做：

WITH OldCTE AS (
    SELECT    customerId, baseCurrencyId, SUM(amount) AS totalOld
    FROM      dbo.OldDebt
    WHERE     (isDeleted = 0)
    GROUP BY  customerId, baseCurrencyId
), RecoveredCTE AS (
    SELECT    customerId, baseCurrencyId, SUM(amount) AS totalRecovered
    FROM      dbo.RecoveredDebt
    WHERE     (isDeleted = 0)
    GROUP BY  customerId, baseCurrencyId
)
SELECT     C.id
FROM       Customer AS C
LEFT JOIN  OldCTE AS OCTE ON OCTE.customerId = C.id
LEFT JOIN  RecoveredCTE AS RCTE ON RCTE.customerId = C.id

Answer 1

如果您想使用 CTE 作为变体：

WITH OldCTE AS (
    SELECT    customerId, baseCurrencyId, SUM(amount) AS totalOld
    FROM      dbo.OldDebt
    WHERE     (isDeleted = 0)
    GROUP BY  customerId, baseCurrencyId
), RecoveredCTE AS (
    SELECT    customerId, baseCurrencyId, SUM(amount) AS totalRecovered
    FROM      dbo.RecoveredDebt
    WHERE     (isDeleted = 0)
    GROUP BY  customerId, baseCurrencyId
)
SELECT C.id,
coalesce(OCTE.totalOld, 0) as totalOldDebt,
coalesce(RCTE.totalRecovered, 0) as totalRecoveredDebt,
coalesce(OCTE.totalOld, 0) - coalesce(RCTE.totalRecovered, 0) as totalDebt
FROM OldCTE AS OCTE
FULL JOIN  RecoveredCTE AS RCTE ON RCTE.customerId = OCTE.customerId and OCTE.baseCurrencyId = RCTE.baseCurrencyId
JOIN Customer as C on C.id = coalesce(OCTE.customerId, RCTE.customerId)