Question

我已经收到一个MySQL查询，用于删除我要添加LIMIT的数以百万计的整数，这也是ORDERS BY ASC。我不知道我在做什么，我很困。

据我了解，您不能限制多表删除，但是我发现解决这个问题的解决方案太复杂了，我无法自行适应。

DELETE a,b,c
FROM wp_posts a
LEFT JOIN wp_term_relationships b ON ( a.ID = b.object_id )
LEFT JOIN wp_postmeta c ON ( a.ID = c.post_id )
LEFT JOIN wp_term_taxonomy d ON ( d.term_taxonomy_id = b.term_taxonomy_id )
LEFT JOIN wp_terms e ON ( e.term_id = d.term_id )
WHERE d.taxonomy = 'edd_log_type' AND a.post_type = 'edd_log' AND e.term_id = 167
ORDER BY ID ASC LIMIT 100;

期望：我正在尝试构建一个查询，该查询将查找和删除最旧的100个条目。我要设置一个LIMIT，因为要处理的条目（百万个）的数量会使查询超时。

实际结果：就我所知，由于LIMIT导致的语法错误不适用于多表删除。

Answer 1

您不应在where子句中使用与左联接表相关的列，因为将其用作内部联接在这些情况下，您应该在ON子句

中移动相关条件

要进行删除（根据您的代码），您可以将delete statemente与查询一起返回所需的100 ID

  delete a,b,c 
  FROM wp_posts a
  LEFT JOIN wp_term_relationships b ON ( a.ID = b.object_id )
  LEFT JOIN wp_postmeta c ON ( a.ID = c.post_id )
  LEFT JOIN wp_term_taxonomy d ON ( d.term_taxonomy_id = b.term_taxonomy_id ) AND d.taxonomy = 'edd_log_type'
  LEFT JOIN wp_terms e ON ( e.term_id = d.term_id ) AND e.term_id = 167
  INNER JOIN  ( 

      select a.id 
      FROM wp_posts a
      LEFT JOIN wp_term_relationships b ON ( a.ID = b.object_id )
      LEFT JOIN wp_postmeta c ON ( a.ID = c.post_id )
      LEFT JOIN wp_term_taxonomy d ON ( d.term_taxonomy_id = b.term_taxonomy_id ) AND d.taxonomy = 'edd_log_type'
      LEFT JOIN wp_terms e ON ( e.term_id = d.term_id ) AND e.term_id = 167
      WHERE a.post_type = 'edd_log'
      ORDER BY ID ASC 
      LIMIT 100

  ) t ON t.id = a.id 
  WHERE AND a.post_type = 'edd_log'

并且正如Strawberry所建议的，使用内部联接更好地进行删除（您不能删除不匹配的行）

  delete a,b,c 
  FROM wp_posts a
  INNER  JOIN wp_term_relationships b ON ( a.ID = b.object_id )
  INNER  JOIN wp_postmeta c ON ( a.ID = c.post_id )
  INNER  JOIN wp_term_taxonomy d ON ( d.term_taxonomy_id = b.term_taxonomy_id ) AND d.taxonomy = 'edd_log_type'
  INNER  JOIN wp_terms e ON ( e.term_id = d.term_id ) AND e.term_id = 167
  INNER JOIN  ( 

      select a.id 
      FROM wp_posts a
      INNER  JOIN wp_term_relationships b ON ( a.ID = b.object_id )
      INNER  JOIN wp_postmeta c ON ( a.ID = c.post_id )
      INNER  JOIN wp_term_taxonomy d ON ( d.term_taxonomy_id = b.term_taxonomy_id ) AND d.taxonomy = 'edd_log_type'
      INNER  JOIN wp_terms e ON ( e.term_id = d.term_id ) AND e.term_id = 167
      WHERE a.post_type = 'edd_log'
      ORDER BY ID ASC 
      LIMIT 100

  ) t ON t.id = a.id 
  WHERE AND a.post_type = 'edd_log'

绝对的初学者，尝试在MySQL中限制和订购DELETE / JOIN查询

1 个答案: