Question

好的，我今天整天都在试着这个问题并且无法解决这个问题，基本上我试图从临时表中随机查询12张照片，其中包含活动登录的所有照片用户尚未投票。

错误显然是＃1137 - 无法重新打开表：＆＃39; r1＆＃39; 哪个临时表只能引用一次。

    CREATE TEMPORARY TABLE unvoted_photos
    SELECT *
    FROM photo
    WHERE photo.photo_uid 
    NOT IN 
    ( SELECT photo_uid
    FROM vote
    WHERE vote.user_uid = '12345' ) ;

    SELECT photo_uid, caption, storage_path
      FROM unvoted_photos AS r1 
      JOIN (SELECT (RAND() * 
                    (SELECT MAX(id)
                    FROM unvoted_photos)) AS sid)
                    AS r2
     WHERE r1.id >= r2.id
     ORDER BY r1.id ASC
     LIMIT 12;

由于性能问题，随机选择查询遵循此example。否则这肯定会奏效。

    SELECT ... FROM photo WHERE photo_uid NOT IN ( voted images subquery ) ORDER BY RAND() LIMIT 12

Answer 1

在对问题的讨论中，这是一种将两者合并在一起的方法，你应该能够立即运行。我用JOIN s重写了这个，但是在这种情况下我将临时表放到子查询中，这样你就可以看到发生了什么。

SELECT photo_uid, caption, storage_path
  FROM (
          SELECT photo_uid, caption, storage_path
          FROM photo
          WHERE photo.photo_uid 
          NOT IN 
          ( 
            SELECT photo_uid
            FROM vote
            WHERE vote.user_uid = '12345' 
          )

       ) r1 
  JOIN (SELECT (RAND() * 
                (SELECT MAX(id)
                FROM unvoted_photos)) AS sid)
                AS r2
 WHERE r1.id >= r2.id
 ORDER BY r1.id ASC
 LIMIT 12;

MySQL：如何解决此查询的临时表错误？

1 个答案: