Mysql don'；t在结果中显示变量

我正在尝试优化此选择，因为如果相同的选择和查询需要两次运行时间，那么：

SELECT sc.ID, 
      (CASE WHEN (SELECT SUM(scu.OK) 
                    FROM `SCU` scu 
                    WHERE scu.ID = _ID
                        AND scu.CCC = sc.ID
                    GROUP BY scu.ISC)
       IS NULL THEN 0 ELSE 
                    (SELECT SUM(scu.OK) 
                    FROM `SCU` scu 
                        WHERE scu.ID = _ID
                            AND scu.CCC = sc.ID
                        GROUP BY scu.ISC)
      END )as 'STATUS'
FROM    ( SELECT `ID` 
            FROM `STORE`
            WHERE `STATE`=1
            ORDER BY `NUMBERIN` DESC) sc
GROUP BY sc.ID;

我试过这样的东西

SELECT sc.ID, 
       @STATUS:=(SELECT SUM(scu.OK) 
                    FROM `SCU` scu 
                    WHERE scu.ID = _ID
                        AND scu.CCC = sc.ID
                    GROUP BY scu.ISC),
      (CASE WHEN @STATUS
       IS NULL THEN 0 ELSE @STATUS
       END ) as 'STATUS'
FROM    ( SELECT `ID` 
            FROM `STORE`
            WHERE `STATE`=1
            ORDER BY `NUMBERIN` DESC) sc
GROUP BY sc.ID;

但它会返回另一列，其中包含@STATUS变量，但它不应该返回。

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结果应具有ID和状态列。有什么想法吗？

最简单的方法是合并，它可以用来用特定的值替换空值

SELECT sc.ID, 
      COALESCE((SELECT SUM(scu.OK) 
                    FROM `SCU` scu 
                    WHERE scu.ID = _ID
                        AND scu.CCC = sc.ID
                    GROUP BY scu.ISC),0) as 'STATUS'      
FROM    ( SELECT `ID` 
            FROM `STORE`
            WHERE `STATE`=1
            ORDER BY `NUMBERIN` DESC) sc
GROUP BY sc.ID;

---

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我认为您可以使用

IFNULL

执行以下操作：

SELECT sc.ID, 
       IFNULL(@STATUS:=(SELECT SUM(scu.OK) 
                    FROM `SCU` scu 
                    WHERE scu.ID = _ID
                        AND scu.CCC = sc.ID
                    GROUP BY scu.ISC),0,@STATUS) AS `STATUS`
FROM    ( SELECT `ID` 
            FROM `STORE`
            WHERE `STATE`=1
            ORDER BY `NUMBERIN` DESC) sc
GROUP BY sc.ID;

这个怎么样

Select 
id, 
      (CASE WHEN status
       IS NULL THEN 0 ELSE status
       END ) as 'STATUS'
from
(SELECT sc.ID, 
       (SELECT SUM(scu.OK) 
                    FROM `SCU` scu 
                    WHERE scu.ID = _ID
                        AND scu.CCC = sc.ID
                    GROUP BY scu.ISC) as status
FROM    ( SELECT `ID` 
            FROM `STORE`
            WHERE `STATE`=1
            ORDER BY `NUMBERIN` DESC) sc
GROUP BY sc.ID) temp

对不起，我在智能手机上输入的。

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希望它比IFNULL更有用。