Question

我有这样的数据库视图：

SELECT e.ExportID, e.Date, SUM(t.Amount) AS TotalAmount
FROM dbo.Exports AS e LEFT OUTER JOIN
dbo.Transactions AS t ON e.TransID = t.TransID
GROUP BY e.ExportID, e.Date, t.Credit

正常工作，返回值。

我需要的是在事务的foreach行中，检查列t.Credit是否为true，如果为true则添加到TotalAmount，如果为false则从TotalAmount中减去？

由于

Answer 1

假设您的t.credit数据类型为布尔值，您可以将总和更改为：

sum(case when t.credit then t.amount else -t.amount end)

Answer 2

SELECT e.ExportID, e.Date, SUM(IF(t.Credit = 'true', t.Amount, -t.Amount)) AS TotalAmount
FROM dbo.Exports AS e LEFT OUTER JOIN
dbo.Transactions AS t ON e.TransID = t.TransID
GROUP BY e.ExportID, e.Date, t.Credit

由于：

SELECT IF('true' = 'true', 1, 0);
+---------------------------+
| IF('true' = 'true', 1, 0) |
+---------------------------+
|                         1 |
+---------------------------+
SELECT IF('true' = 'false', 1, 0);
+----------------------------+
| IF('true' = 'false', 1, 0) |
+----------------------------+
|                          0 |
+----------------------------+

理由：

SELECT SUM(IF(t.Credit = 'true', t.Amount, -t.Amount))
FROM (
    SELECT 1 AS Amount, 'true' AS Credit
    UNION
    SELECT 2 AS Amount, 'false' AS Credit
    UNION
    SELECT 5 AS Amount, 'true' AS Credit
) t;

结果：

+-------------------------------------------------+
| SUM(IF(t.Credit = 'true', t.Amount, -t.Amount)) |
+-------------------------------------------------+
|                                               4 |
+-------------------------------------------------+

Sql View根据另一列计算列

2 个答案: