Select 给定年份所有月份的记录形成第一个 table 和第二个 table 的记录

Question

我的数据库中有两个 table：

MembershipInstallments（ProjectId、AllotmentId、InstallmentId、EntryDate、AmountPaid）
Memberships (ProjectId, AllotmentId, ClientId, ClientName, RegistrationNo)

我想 select 客户在一年内按月付款。以及当年年初之前支付的金额。我想要的结果集是

假设 2019 年：

ClientName, RegistrationNumbers, PreviouslyPaidAmount (i.e. all amounts paid in 2018), AmountPaidInJuly 2019, AmountPaidInAugust2019. ..... AmountPaidIn Jun2020

其中月份是 EntryDate 来自 MembershipInstallments table。

我是这样试过的，但是对于大数据集耗时太长：

SELECT 
    ClientName, RegistrationNo,
    (SELECT ISNULL(SUM(AmountPaid),0)
     FROM MembershipInstallments 
     WHERE ProjectId = Membership.ProjectId 
       AND AllotmentId = Membership.AllotmentId 
       AND EntryDate < @fromDate) ASPreviouslyPaid,
    (SELECT ISNULL(SUM(AmountPaid), 0)
     FROM MembershipInstallments 
     WHERE ProjectId = Membership.ProjectId 
       AND AllotmentId = Memberhsip.AllotmentId 
       AND (MONTH(EntryDate) = 7) AND (YEAR(EntryDate) = YEAR(@fromDate)) AS JulyPayment
FROM 
    Memberships 
WHERE 
    ProjectId = @projectId

任何帮助将不胜感激。

Answer 1

标量子查询 往往优化不佳。在你的情况下（相同的加入条件）你可以简单地利用 conditional aggregation:

SELECT ms.ClientName,ms.RegistrationNo,
   Sum(CASE WHEN mi.EntryDate<@fromDate THEN mi.AmountPaid ELSE 0 end) AS PreviouslyPaid,
   Sum(CASE WHEN (Month(mi.EntryDate) = 7) AND (Year(mi.EntryDate) = Year(@fromDate)) THEN mi.AmountPaid ELSE 0)
FROM Memberships AS ms
LEFT JOIN MembershipInstallments AS mi -- don't know if Outer join is really needed
  ON mi.ProjectId=ms.ProjectId
  AND mi.AllotmentId=ms.AllotmentId
WHERE ms.ProjectId=@projectId

您可以在加入之前进行聚合，即在 CTE 中进一步提高性能：

WITH cte AS
 (
   SELECT  
      ProjectId, AllotmentId,
      Sum(CASE WHEN EntryDate<@fromDate THEN AmountPaid ELSE 0 END) AS PreviouslyPaid,
      Sum(CASE WHEN (Month(EntryDate) = 7) AND (Year(EntryDate) = Year(@fromDate)) THEN AmountPaid ELSE 0 END) AS JulyPayment
   FROM MembershipInstallments 
   WHERE ProjectId=@projectId
   GROUP BY ProjectId, AllotmentId
 )
SELECT ms.ClientName, ms.RegistrationNo, cte.PreviouslyPaid, cte.JulyPayment
FROM Memberships AS ms
JOIN cte
  ON cte.ProjectId=ms.ProjectId
  AND cte.AllotmentId=ms.AllotmentId
WHERE ms.ProjectId=@projectId

在这两种情况下仔细检查结果是否正确（取决于这些表之间的实际关系）

Select 给定年份所有月份的记录形成第一个 table 和第二个 table 的记录

Select Records against all months of a given year form one table with records from second table

sql

tsql

database

sql-server-2014