mysql - 如何访问子查询中的列？

Question

我对以下查询有疑问。对于返回总结果总和的子查询，我收到错误Unknown column 'search.term' in 'where clause'，我不确定如何正确执行此查询？任何帮助表示赞赏。

SELECT *,
  (SELECT SUM(totalResults)
   FROM (SELECT COUNT(*) as totalResults
         FROM media
         LEFT JOIN users ON users.id = media.userId
         WHERE media.title LIKE CONCAT('%', search.term, '%')
       OR media.description LIKE CONCAT('%', search.term, '%')
       OR media.tags LIKE CONCAT('%', search.term, '%')
       OR users.username LIKE search.term
         UNION ALL
         SELECT COUNT(*)
         FROM reposts
         LEFT JOIN media ON media.id = reposts.mediaId
         LEFT JOIN users ON users.id = reposts.userId
         WHERE media.title LIKE CONCAT('%', search.term, '%')
       OR media.description LIKE CONCAT('%', search.term, '%')
       OR media.tags LIKE CONCAT('%', search.term, '%')
       OR users.username LIKE search.term
         )
  t) AS totalResults,
  MAX(search.timestamp) AS searchTimestamp
  FROM search
  WHERE userId = '1'
  GROUP BY search.term
  ORDER BY searchTimestamp DESC

Answer 1

原因是双重嵌套的SELECT子查询。尝试这个：

 SELECT  term,
         ( SELECT COUNT(*)
           FROM media
           LEFT JOIN users ON users.id = media.userId
           WHERE media.title LIKE CONCAT('%', search.term, '%') 
              OR media.description LIKE CONCAT('%', search.term, '%') 
              OR media.tags LIKE CONCAT('%', search.term, '%') 
              OR users.username LIKE search.term
         )
         +
         ( SELECT COUNT(*)
           FROM reposts
           LEFT JOIN media ON media.id = reposts.mediaId
           LEFT JOIN users ON users.id = reposts.userId
           WHERE media.title LIKE CONCAT('%', search.term, '%') 
              OR media.description LIKE CONCAT('%', search.term, '%') 
              OR media.tags LIKE CONCAT('%', search.term, '%') 
              OR users.username LIKE search.term
         ) AS totalResults,
         MAX(timestamp) AS searchTimestamp
FROM search
WHERE userId = '1'
GROUP BY term
ORDER BY searchTimestamp DESC ;

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旁注：使用SELECT *while haveGROUP BY <columns>将在所有其他列中为您提供不确定的结果，除了<columns>. MySQL 允许这种定义不明确的行为，但这不是一个好的做法。