GROUP BY 并为分组的每个唯一值创建列（始终输出为 1 行），然后将输出用作 JOIN - SQL Server

Question

我需要按 2 列（BillingId 和 PaymentType）对数据进行分组 - 没有问题，并且输出 1 行，其中包含唯一的 PaymentType 列- 此步骤存在问题。因此，每个 BillingId 只有 1 行，该表将用于连接数据库中的另一个表。

计费表：

BillingId (unique)

 12345
 67890

付款表：

PaymentId PaymentType  BillingId PaymentAmount
 (unique)

   12      electronic    12345      62.29
   14      electronic    12345      73.28
   56      electronic    12345     -62.29
   6       electronic    67890      83.58
   2       adjustment    67890      30.43

我的代码：

SELECT GroupedTable.* 

FROM (SELECT b.BillingId, 
             p.PaymentType, 
             SUM(p.PaymentAmount) AS AmountPaid
      FROM Billing AS b
      LEFT JOIN Payment AS p
        ON (b.BillingId = p.BillingId)
      GROUP BY b.BillingId, p.PaymentType) AS GroupedTable

输出（显然不正确）：

  BillingId  PaymentType   AmountPaid

     67890    electronic    83.58
     12345    electronic    73.28
     67890    adjustment    30.43

我需要的输出：

BillingId    AmountPaid     AmountAdjusted 
            (electronic)     (adjustment)

  67890         83.58           30.43
  12345         73.28            0

Answer 1

如果使用Case When如下表达式，看起来会更容易：

Select B.BillingId, Sum(Case When P.PaymentType='electronic' Then P.PaymentAmount End) As [AmountPaid (electronic)],
                    Sum(Case When P.PaymentType='adjustment' Then P.PaymentAmount End) As [AmountAdjusted (adjustment)] 
From Billing As B Left Join Payment As P On (B.BillingId=P.BillingId)
Group by B.BillingId

数据库<>小提琴

帐单ID	支付金额（电子）	调整金额（调整）
12345	73,28	无效的
67890	83,58	30,43