MySQL和case語句不起作用

Question

/*-------------temp table--------------*/
CREATE TEMPORARY TABLE IF NOT EXISTS bowlpick.tempschedule AS

(SELECT * FROM bowlpick.schedule

where season = (select max(year) from bowlpick.season));
/*-------------temp table--------------*/

set @g1= (select winner from bowlpick.tempschedule where game =1);

select date,name, @g1,bowl1 Pick,comf1

,case 
    when bowl1 =  @g1 then  comf1 
    when bowl1 <> @g1 then -comf1 
else '0' end pts

from bowlpick.picks
where year(date) = (select max(year) from bowlpick.season)
order by bowl1 desc limit 5



<--------------------Table----------------->
  name      @g1            Pick       comf1 pts
Player 1    Boise State     Washington  7   -7
Player 2    Boise State     Boise State 30  -30
Player 3    Boise State     Boise State 21  -21
Player 4    Boise State     Boise State 27  -27
Player 5    Boise State     Boise State 15  -15

為什么這不起作用？？？ 最后四個點應為正數，而不是負數。 好像變量（@ g1）在'CASE'部分中不起作用。 當“選擇”部分時，它可以正常工作。 如果我對獲勝者（博伊西州）進行了硬編碼，則它可以正常工作。 變量在case語句中不起作用嗎？

Answer 1

不知道為什么要使用臨時表，可以在單個查詢中進行操作，請參見下面的示例以了解開始的地方，我注意到的另一件事是該案例返回了兩個case語句的數字和else的字符串。 不僅如此，case語句還有2個WHEN語句，這些語句肯定覆蓋了所有基數，這意味着永遠不會選擇“ 0”。

SELECT 
    bowlpick.picks.date
    ,bowlpick.picks.name
    ,bowlpick.tempschedule.winner
    ,bowlpick.picks.bowl1 Pick
    ,bowlpick.picks.comf1
    ,CASE 
        WHEN bowlpick.picks.bowl1 =  bowlpick.tempschedule.winner  THEN bowlpick.picks.comf1 
        WHEN bowlpick.picks.bowl1 <> bowlpick.tempschedule.winner  THEN -bowlpick.picks.comf1 
        ELSE 0
    END pts
FROM 
    bowlpick.picks
    LEFT JOIN bowlpick.tempschedule ON year(bowlpick.picks.date) = bowlpick.tempschedule.season 
WHERE 
    bowlpick.tempschedule.game =1
ORDER BY 
    bowl1 DESC
LIMIT 5

以下是一些額外的工作，消除了對臨時表的需要（鏈接和分組將需要更好地定義，但是對於不完整的架構，這是我所能做的最好的事情）

SELECT 
    p.Date
    ,p.Name
    ,s.Winner
    ,p.Bowl1 Pick
    ,p.Comf1
    ,CASE 
        WHEN p.Bowl1 =  s.Winner  THEN p.Comf1 
        WHEN p.Bowl1 <> s.Winner  THEN -p.Comf1 
        ELSE 0
    END pts
FROM 
    picks p
    LEFT JOIN schedule s ON YEAR(p.Date) = s.Season 
WHERE 
    s.game = 1
GROUP BY 
    s.Season, p.Date
HAVING
    s.Season = MAX(s.Season)
ORDER BY 
    p.Bowl1 DESC
LIMIT 5

他是我的SQL提琴演奏者