sql - 复杂的查询使网站速度极慢

Question

 select SQL_CALC_FOUND_ROWS DISTINCT media.*, username 
from album as album, album_permission as permission, user as user, media as media , word_tag as word_tag, tag as tag 
where ((media.album_id = album.album_id and album.private = 'yes' and album.album_id = permission.album_id and (permission.email = '' or permission.user_id = '') ) or (media.album_id = album.album_id and album.private = 'no' ) or media.album_id = '0' ) 
and media.status = '1' 
and media.user_id = user.user_id 
and word_tag.media_id = media.media_id 
and word_tag.tag_id = tag.tag_id 
and tag.name in ('justin','bieber','malfunction','katherine','heigl','wardrobe','cinetube') and media.media_type = 'video' 
and media.media_id not in ('YHL6a5z8MV4') 
group by media.media_id 
order by RAND()
#there is limit too, by 20 rows..

我不知道从哪里开始解释这个问题，但是请原谅我，如果您有任何问题，请询问我。以下是解释。

SQL_CALC_FOUND_ROWS 正在计算有多少行并将用于分页，因此它会计算总记录，即使只显示 20 条。

DISTINCT 将停止显示重复的行。

用户名来自用户表。

相册，album_permission。它检查相册是否是私有(private)的，如果是，则通过 user_id 检查用户是否有权限。

我认为休息很容易理解，但如果您需要了解更多，请询问。

我对此查询感到非常沮丧，并且由于此查询，网站有时非常慢或无法打开。请帮忙

SQL query: EXPLAIN select SQL_CALC_FOUND_ROWS DISTINCT media.*, username from album as album, album_permission as permission, user as user, media as media , word_tag as word_tag, tag as tag where ((media.album_id = album.album_id and album.private = 'yes' and album.album_id = permission.album_id and (permission.email = '' or permission.user_id = '') ) or (media.album_id = album.album_id and album.private = 'no' ) or media.album_id = '0' ) and media.status = '1' and media.user_id = user.user_id and word_tag.media_id = media.media_id and word_tag.tag_id = tag.tag_id and tag.name in ('justin','bieber','malfunction','katherine','heigl','wardrobe','cinetube') and media.media_type = 'video' and media.media_id not in ('YHL6a5z8MV4') group by media.media_id order by RAND() ;
Rows: 6
id  select_type  table  type  possible_keys  key  key_len  ref  rows  Extra
1  SIMPLE  permission  system  album_id  NULL  NULL  NULL  1  Using temporary; Using filesort
1  SIMPLE  album  ALL  PRIMARY  NULL  NULL  NULL  68   
1  SIMPLE  word_tag  ALL  media_id  NULL  NULL  NULL  88383  Using where; Using join buffer
1  SIMPLE  media  eq_ref  media_id,album_id  media_id  34  _site.word_tag.media_id  1  Using where
1  SIMPLE  tag  eq_ref  PRIMARY  PRIMARY  4  _site.word_tag.tag_id  1  Using where
1  SIMPLE  user  eq_ref  PRIMARY  PRIMARY  34  _site.media.user_id  1   

表结构http://pastie.org/912388这个链接有表转储，您可以在 phpmyadmin 中执行或运行它并查看表的结构。

Answer 1

您能做的最好的事情就是运行查询，但在其前面放置一个EXPLAIN，然后分析结果。

如果不知道该查询中所有表的结构(尤其是索引)，我们将很难给您一个好的答案。

从这里开始:Optimizing Queries with EXPLAIN .

如果您按照此处的建议无法取得任何进展，请发布您的表格结构，我们也许可以为您提供帮助。