使用SQL Server从贷方和借方导出期末余额

我认为您不需要LAG()，只需打开窗口即可SUM()：

CREATE TABLE Data (
    cust int, 
    [date] date, 
    [credit amount] numeric(10, 2), 
    [debit amount] numeric(10, 2)  
)
INSERT INTO Data 
    (cust, [date], [credit amount], [debit amount])
VALUES
    (1, '20200101',   5000.00,      0.00),  
    (2, '20200101',      0.00,      2000.00),   
    (2, '20200107',   4000.00,      0.00),
    (1, '20200107',      0.00,      2000),   
    (1, '20200109',   5000.00,      0.00)

声明：

SELECT 
    cust, [date], [credit amount], [debit amount], 
    SUM(-[debit amount] + [credit amount]) OVER (PARTITION BY cust ORDER BY [date]) AS [closing balance]
FROM Data