SQL在現有記錄之間插入行

Question

我有一張表格，其中只有貸款的記錄對應於它們被取出和償還的具體日期 - 即每筆貸款兩筆記錄。

Loans 

Loan ID | Month  | Rate | Action 
-------------------------------- 
1  | 5/1/2000 | 5.50% | New 
1  | 9/1/2000 | 6.00% | Closed 
2  | 3/1/2000 | 5.25% | New 
2  | 5/2/2000 | 5.50% | Closed 

我有另一個利率記錄每個日期。

Interest rates 

Month  | Rate 
-------------------- 
1/1/2000 | 5.00% 
2/1/2000 | 5.25% 
3/1/2000 | 5.25% 
4/1/2000 | 5.25% 
5/1/2000 | 5.50% 
6/1/2000 | 5.50% 
7/1/2000 | 5.50% 
8/1/2000 | 6.00% 
9/1/2000 | 6.00% 
10/1/2000 | 6.50% 

我想插入行對當給定貸款取出，歸還之間的貸款表丟失時間（和相應的利率）。鑑於中間日期需要插入的每一筆貸款，我一直沒能解決這個與LEFT JOIN，MERGE等

預期的結果：使硬

Loan ID | Month  | Rate | Action 
--------------------------------- 
1  | 5/1/2000 | 5.50% | New 
1  | 6/1/2000 | 5.50% | NULL 
1  | 7/1/2000 | 5.50% | NULL 
1  | 8/1/2000 | 6% | NULL 
1  | 9/1/2000 | 6% | Closed 
2  | 3/1/2000 | 5.25% | New 
2  | 4/1/2000 | 5.25% | NULL 
2  | 5/1/2000 | 5.50% | Closed 

Answer 1

Numbers表格往往是有幫助的，當你需要生成日期序列行。它只是一個包含大量整數序列的表格。你可以閱讀如何創建一個here（以及其他地方）。一旦你在的地方，你可以使用這樣的查詢（這是SQL Server）：

;with cteLoan as(
select t1.LoanID, min(t1.Month) StartDate, max(t1.Month) EndDate 
from Table1 t1 
group by t1.LoanID 
) 

select c.LoanID, dateadd(month, n.Number, c.StartDate) Month, t2.Rate, null Action 
from Numbers n 
cross join cteLoan c 
join Table2 t2 on t2.Month = dateadd(month, n.Number, c.StartDate) 
where n.Number >= 0 and n.number < DATEDIFF(month, c.StartDate, c.EndDate) 

union 

select t1.LoanID, t1.Month, t1.Rate, t1.Action 
from Table1 t1 
order by LoanID, Month 

要結果插入另一張表，你應該能夠做到：

insert into Results(LoadID, Month, Rate, Action) 
select c.LoanID, dateadd(month, n.Number, c.StartDate) Month, t2.Rate, null Action 
from Numbers n 
cross join cteLoan c 
join Table2 t2 on t2.Month = dateadd(month, n.Number, c.StartDate) 
where n.Number >= 0 and n.number < DATEDIFF(month, c.StartDate, c.EndDate) 

union 

select t1.LoanID, t1.Month, t1.Rate, t1.Action 
from Table1 t1 
order by LoanID, Month 

Answer 2

您的設計和你沒有說你正在使用什麼數據庫。下面是SQL Server中的樣品（查詢也將PostgreSQL的工作）：

DECLARE @loans TABLE 
    (
     LoanID INT , 
     [Month] DATETIME , 
     Rate DECIMAL(4, 2) , 
     [Action] VARCHAR(10) 
    ); 

INSERT @loans 
     (LoanID, Month, Rate, Action) 
VALUES (1, '5/1/2000', 5.50, 'New '), 
     (1, '9/1/2000', 6.00, 'Closed '), 
     (2, '3/1/2000', 5.25, 'New '), 
     (2, '5/2/2000', 5.50, 'Closed '); 


DECLARE @rates TABLE 
    (
     Month DATETIME , 
     Rate DECIMAL(4, 2) 
    ); 
INSERT @rates 
     (Month, Rate) 
VALUES ('1/1/2000', 5.00), 
     ('2/1/2000', 5.25), 
     ('3/1/2000', 5.25), 
     ('4/1/2000', 5.25), 
     ('5/1/2000', 5.50), 
     ('6/1/2000', 5.50), 
     ('7/1/2000', 5.50), 
     ('8/1/2000', 6.00), 
     ('9/1/2000', 6.00), 
     ('10/1/2000', 6.50); 

WITH loanStart 
      AS (SELECT * 
       FROM  @loans 
       WHERE Action = 'New' 
      ), 
     loanEnd 
      AS (SELECT * 
       FROM  @loans 
       WHERE Action = 'Closed' 
      ), 
     loanRanges (loanId, lStart, lEnd) 
      AS (SELECT ls.LoanID , 
         ls.Month , 
         le.Month 
       FROM  loanStart ls 
         INNER JOIN loanEnd le ON ls.LoanID = le.LoanID 
      ) 
    SELECT lr.loanId , 
      r.Month , 
      r.Rate , 
      COALESCE(ls.Action, le.Action) AS action 
    FROM @rates r 
      INNER JOIN loanRanges lr ON r.Month >= lr.lStart 
             AND r.Month <= lr.lEnd 
      LEFT JOIN loanStart ls ON ls.LoanID = lr.loanId 
             AND YEAR(ls.Month) = YEAR(r.Month) 
             AND MONTH(ls.Month) = MONTH(r.Month) 
      LEFT JOIN loanEnd le ON le.LoanID = lr.loanId 
            AND YEAR(le.Month) = YEAR(r.Month) 
            AND MONTH(le.Month) = MONTH(r.Month) 
    ORDER BY lr.loanId , 
      r.Month;