SQL将变量传递给子查询

Question

我无法将变量传递给子查询。

我有2个不同的表需要得到所有采访人员。

现在我的SQL

SELECT 
    empl.id AS id, 
    (SELECT 
     GROUP_CONCAT(interviewed_by SEPARATOR ', ') 
     FROM 
     (
      SELECT 
       interview_old.interviewed_by 
      FROM 
       interview_old 
      WHERE 
       interview_old.empl = empl.id 

      UNION 

      SELECT 
       interview.interviewed_by 
      FROM 
       interview 
      WHERE 
       interview.empl = empl.id 
     ) 
     as interviewed_by 
    ) AS interviews 
FROM 
    empl AS empl 

这不是我完整的代码，所以我不能改变这部分

SELECT 
    empl.id AS id, 
    {only here allow insert custom sql} 
FROM 
    empl AS empl 

Answer 1

你的问题是不是100％清楚，但你可以通过启动将您的quesry转换为不使用子查询，但只需要LEFT JOIN与GROUP：

SELECT 
    empl.id AS id, 
    GROUP_CONCAT(i.interviewed_by SEPARATOR ', ') 
FROM 
    empl AS empl 
LEFT JOIN (
    SELECT empl, interviewed_by 
    FROM interview_old 
    UNION 
    SELECT empl, interviewed_by 
    FROM interview 
) i 
ON i.empl = empl.id 
GROUP BY empl.id 

Answer 2

您需要从子查询中获得想要的结果，然后将整个事件与主表empl合并，然后通过empid进行分组。

SELECT 
     empl.id AS id, GROUP_CONCAT(interviewed_by SEPARATOR ', ') 
     FROM 
      (SELECT interview_old.empl employeeid, interview_old.interviewed_by as interviewed_by FROM interview_old 
        UNION 
      SELECT interview.empl,interview.interviewed_by 
        FROM interview) as tmp join empl AS empl on (empl.id=tmp.employeeid) 
        group by empl.id