选择前一行并计算

Question

我有两张桌子

1. 贷款
2. Loan_Payments
MS Access
中的

贷款包括

1. Ref_Loan
2. Amount_Loan

Loan_Payments包括

1. Ref_Loan
2. Amount_Paid
3. 日期

贷款表

Ref_Loan    Loan_Amount
loan 1      12000
loan 2      24000
loan 3      5000 

Loan_Payments

Ref_Loan Amount_Paid Date
loan 1     1000    01/01/2011
loan 1     1000    01/02/2011
loan 1     1000    01/03/2011
loan 2     1000    01/01/2011
loan 2     1000    01/02/2011

我想要一个像这样展示的外线;

Ref_loan    Amount_Paid    Date      Balance
loan 1      1000         01/01/2011  11000
loan 1      1000         01/02/2011  10000
loan 1      1000         01/03/2011   9000
loan 2      1000         01/01/2011  23000
loan 2      1000         01/02/2011  22000
loan 3                                5000

Answer 1

访问查询：

select L.Ref_Loan, P.Amount_Paid, P.Date,
    L.Loan_Amount - DSum("Amount_Paid", "Loan_Payment",
    "Ref_Loan=" & L.Ref_Loan & " AND Date<= #" & Format(P.Date, "yyyy/mm/dd") & "#")
from Loan AS L
left join Loan_Payments AS P on P.Ref_Loan = L.Ref_Loan
ORDER BY L.Ref_Loan, P.Date

但是，如果您使用的是来自C＃的Jet，则DSum可能无法正常工作。在这种情况下，请完整地写出正确的SQL

select L.Ref_Loan, P.Amount_Paid, P.Date,
    L.Loan_Amount - (
        SELECT SUM(P2.amount_paid)
        FROM Loan_Payment AS P2
        WHERE P2.Ref_Loan=L.Ref_Loan
        AND P2.Date <= P.Date)
from Loan AS L
left join Loan_Payments AS P on P.Ref_Loan = L.Ref_Loan
ORDER BY L.Ref_Loan, P.Date