T-Sql Sum 正负浮点值

Question

WITH CTE AS
(
    SELECT 
        ITM.CODE AS ITMCODE,
        CASE 
           WHEN IOCODE IN (1,2) THEN AMOUNT 
           ELSE AMOUNT * -1 
        END AS AMOUNT
    FROM 
        ITEMLINE ITL, ITEMS ITM 
    WHERE 
        ITL.ITEMREF = ITM.LOGICALREF 
        AND ITM.CODE = '123'
)
SELECT 
    ITMCODE, SUM(AMOUNT)  
FROM 
    CTE 
GROUP BY 
    ITMCODE

从 CTE 返回 5 行，数量为 float 类型。 Sum 函数返回 2,27373675443232E-13。如果我不使用 Amount * -1 没有问题，返回值是正常的。是什么原因造成的？这从一个视图返回，我不能改变它被禁止的视图，我必须修复这些值。五行的值是 5,6,7,8,9。谢谢。

Answer 1

首先，您的查询太复杂了。做吧：

SELECT ITM.CODE AS ITMCODE,
       SUM(CASE WHEN IOCODE IN (1, 2) THEN AMOUNT ELSE AMOUNT * -1 
           END) AS AMOUNT
FROM ITEMLINE ITL JOIN
     ITEMS ITM 
     ON ITL.ITEMREF = ITM.LOGICALREF 
WHERE ITM.CODE = '123'
GROUP BY ITM.CODE;

其次，这是浮点数的本质。您应该将金额存储为decimal/numeric，定点数。

你应该可以通过转换为合适的类型得到你想要的：

SELECT ITM.CODE AS ITMCODE,
       CONVERT(DECIMAL(10, 2),  -- or whatever
               SUM(CASE WHEN IOCODE IN (1, 2) THEN AMOUNT ELSE AMOUNT * -1 
                   END)
              ) AS AMOUNT
FROM ITEMLINE ITL JOIN
     ITEMS ITM 
     ON ITL.ITEMREF = ITM.LOGICALREF 
WHERE ITM.CODE = '123'
GROUP BY ITM.CODE;

但是，我建议您修复表中的数据，以便以更适合货币金额的方式存储金额，因此：

alter table itemline alter column amount decimal(12, 4);  -- or whatever