mysql - SQL将变量传递给子查询

我无法将变量传递给子查询。

我有2个不同的表，需要让所有采访人员参加。

当前我的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

这不是我的完整代码，所以我无法更改此部分

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

最佳答案

您的问题不是100％清楚，但是您可以首先将查询转换为不使用子查询，而仅将LEFT JOIN与GROUP结合使用：

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