Question

不幸的是，SQL并不是很容易找到我。我有两个表，一个Loan表和一个LoanPayments表。

LoanPayments表：

ID（主键），LoanID（与贷款表上的ID匹配），PaymentDate，Amount等。

我需要一个sql语句，可以给我每个月输入的最后一笔付款（如果有的话）。我目前的陈述并没有给我结果。还有一个问题是，有时候那个月的最大日期会有一个平局，所以我也需要能够处理这个问题（我的想法是在平局的情况下选择最大的ID）。

这是我到目前为止（我知道这是错的，但我不知道为什么。）：

SELECT lp.ID, lp.LoanID, lp.PaymentDate 
FROM LoanPayments lp 
WHERE lp.PaymentDate in (
                          SELECT DISTINCT MAX(PaymentDate) as PaymentDate 
                          FROM LoanPayments 
                          WHERE IsDeleted = 0
                          AND ReturnDate is null 
                          GROUP BY YEAR(PaymentDate), Month(PaymentDate)
                        ) 
AND CAST(PaymentDate as date) >= CAST(DATEADD(mm, -24, GETDATE()) as date)

最后一部分只是过滤它，所以我只收到过去24个月的付款。感谢您的帮助，并花时间帮我解决这个问题。

Answer 1

您可以在此处使用ROW_NUMBER（）函数：

SELECT *
FROM (SELECT lp.ID, lp.LoanID, lp.PaymentDate
          , ROW_NUMBER() OVER (PARTITION BY YEAR(PaymentDate), Month(PaymentDate) ORDER BY PaymentDate DESC) 'RowRank'
      FROM LoanPayments lp 
     )sub
WHERE RowRank = 1

这只是每个月最近的PaymentDate，如果你想通过LoanID，你可以将LoanID添加到PARTITION BY列表中。如果您对保留关系感兴趣，可以使用RANK()代替ROW_NUMBER()

Answer 2

步骤1：使用窗口函数添加按月保存最大PaymentDate的列

SELECT
  ID,
  LoanID,
  PaymentDate,
  MAX(PaymentDate) OVER(PARTITION BY YEAR(PaymentDate), MONTH(PaymentDate)) AS MaxPaymentDate,
  ROW_NUMBER() OVER(PARTITION BY PaymentDate ORDER BY ID) AS TieBreaker
FROM LoanPayments 
WHERE IsDeleted = 0
AND ReturnDate is null

第2步：将这些结果过滤到您想要的行

SELECT ID,LoanID,PaymentDate
FROM (
  SELECT
    ID,
    LoanID,
    PaymentDate,
    MAX(PaymentDate) OVER(PARTITION BY YEAR(PaymentDate), MONTH(PaymentDate)) AS MaxPaymentDate,
    ROW_NUMBER() OVER(PARTITION BY PaymentDate ORDER BY ID) AS TieBreaker
  FROM LoanPayments 
  WHERE IsDeleted = 0
  AND ReturnDate is null
) t1
WHERE PaymentDate = MaxPaymentDate AND TieBreaker = 1

此方法比进行自联接更有效。

从每个月获取最后记录

2 个答案: