SQL UPDATE将一列设置为另一个值并在同一步骤中更改值

Question

请参阅以下更新声明.

UPDATE  TABLE_1
SET     Units2 = ABS(Units1)
        ,Dollars2=ABS(Dallars1)
        ,Units1 =0
        ,Dollars1 =0
WHERE Units1 < 0
AND   Dollars2 = 0

这是我的问题,

1)这合法吗？它解析并"似乎"工作(在测试表上),但它是否总是有效,或者我只是选择正确的记录进行审核.

2)有更好的方法来做到这一点.

谢谢,

Answer 1

因为你是想基本上保持旧值是合法的,只要Units1和Dollars1中Units2和Dollars2应工作

这是一个测试:

CREATE TABLE #Table_1
(
    Units1 INT,
    Dollars1 MONEY,
    Units2 INT,
    Dollars2 MONEY
)
GO

INSERT INTO #Table_1 (Units1, Dollars1, Units2, Dollars2)
VALUES (-1,12.00,3,0.00)
GO

UPDATE  #TABLE_1
SET     Units2 = ABS(Units1)
        ,Dollars2=ABS(Dollars1)
        ,Units1 =0
        ,Dollars1 =0
WHERE Units1 < 0
AND   Dollars2 = 0
GO

SELECT * 
FROM  #Table_1

输出:

Units1 | Dollars1 | Units2| Dollars2
0      | 0.00     | 1     | 12.00