mysql - SQL 返回错误总数

Question

我有这个数据库:

我有这个 sql:(黑色和白色)

SELECT 
    SUM(XS) AS TotalXS 
FROM 
    (SELECT XS 
     FROM `bng` 
     WHERE Color = 'White' 
       AND Action = 'Add' OR Action = 'Transfer Location' 

     UNION ALL 

     SELECT (XS*-1) AS GetXS 
     FROM `bng` 
     WHERE Color = 'White' AND Action = 'Used/ Damaged') AS FinalXS

我的问题是:此 SQL 仅返回“WHITE”的错误总数。查看下面的结果:

对于所有列，White 的结果都应该是“13”。我试图找到解决方案，但没有一个对我有用。我也想知道我是否做错了什么。希望你们能帮我解决这个问题。

Answer 1

问题是第一个子查询中缺少括号和(缺少)运算符优先级:

WHERE Color = 'White' 
    AND Action = 'Add' OR Action = 'Transfer Location' 

你可能希望这是

WHERE Color = 'White' 
    AND ( Action = 'Add' OR Action = 'Transfer Location' )

而数据库将其解释为

WHERE ( Color = 'White' AND Action = 'Add' )
    OR Action = 'Transfer Location'