SQL返回错误的总数

Question

我有这个数据库：

我有这个sql :(黑白两种）

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：这个SQL返回错误的总数为＆＃34; WHITE＆＃34;只要。见下面的结果：

White的结果应为＆＃34; 13＆＃34;对于所有列。我试图找到解决方案，但它们都不适合我。我也想知道我做错了什么。希望你们能帮助我解决这个问题。

Answer 1

问题是在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' 

您可能希望这是

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' 

Answer 2

你可以试试这个

SELECT  COLOR, 
   SUM( CASE WHEN ACTION IN ('Add', 'Transfer Location') THEN XS ELSE -XS END ) AS SUM_XS
FROM BNG
WHERE ACTION IN  ('Add', 'Transfer Location', 'Used/ Damaged')
GROUP BY COLOR

或另一个版本（以避免重复案例......）：

SELECT COLOR
, SUM(XS*SIGN) AS SUM_XS
, SUM(SM*SIGN) AS SUM_SM
FROM (
    SELECT COLOR, XS, SM 
           , CASE WHEN ACTION IN ('Add', 'Transfer Location') THEN 1 ELSE -1 END AS SIGN   
    FROM BNG
     WHERE ACTION IN  ('Add', 'Transfer Location', 'Used/ Damaged')
    ) A
GROUP BY COLOR;