在DB2中查找和求和合約SQL

Question

我正試圖計算下表中的合同修正值。

時，有一個修訂的合同值與從合同的最後一個版本+在修改增加值餘數更新。 爲了說明我添加了如何在最後一列計算的信息。

我該如何解決DB2中的SQL問題，我在這裏打了一堵牆。 謝謝

Answer 1

考慮使用自己加入每個計算運行號合同與ROW_NUMBER()。具體而言，將LEFT JOIN過濾爲第一個FROM表後面的一個行號。從那裏列將用於AmendmentValue計算對齊：除了單元格引用的

SELECT sub1.Contract, sub1.Amendment, sub1.Value, sub1.Billed, sub1.Reminder, 
     (CASE WHEN sub1.Amendment IS NULL THEN NULL 
     ELSE sub1.Billed - sub2.Remainder END) As AmendmentValue 
FROM 
    (SELECT t.Contract, t.Amendment, t.Value, t.Billed, t.Remainder, 
      ROW_NUMBER() OVER (PARTITION BY t.Contract 
      ORDER BY CASE WHEN t.Amendment IS NULL THEN 1 ELSE t.Amendment END) rn 
     FROM TableName t) sub1 
LEFT JOIN 
    (SELECT t.Contract, t.Amendment, t.Value, t.Billed, t.Remainder, 
      ROW_NUMBER() OVER (PARTITION BY t.Contract 
      ORDER BY CASE WHEN t.Amendment IS NULL THEN 1 ELSE t.Amendment END) rn 
     FROM TableName t) sub2 
ON sub1.Contract = sub2.Contract AND sub1.rn = sub2.rn + 1