Question

我需要在将表连接到其他表之前对其进行聚合。

wp_postmeta GROUP BY wp_postmeta.post_id

有可能吗？我应该把它放在哪里？这是我的代码：

SELECT wp_posts.post_content, wp_posts.ID, wp_terms.slug
FROM wp_posts
JOIN wp_postmeta ON wp_posts.ID = wp_postmeta.post_id
JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
JOIN wp_term_taxonomy ON wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
JOIN wp_terms ON wp_term_taxonomy.term_id = wp_terms.term_id


WHERE wp_posts.post_type = 'my-type'
   AND wp_posts.post_status = 'publish'
   AND wp_terms.slug IN
      ('field1', 'field2', 'field3')
   AND
   (
        wp_postmeta.meta_key = 'exclude' AND wp_postmeta.meta_value <> '111'
        OR wp_postmeta.meta_key = 'include' AND wp_postmeta.meta_value = '22'
        OR wp_postmeta.meta_key <> 'include' AND wp_postmeta.meta_key <> 'exclude'
   )

在测试ruakh示例时找到了一种新方法。我不知道它为什么会起作用，但确实如此：

SELECT wp_posts.post_content, wp_posts.ID, wp_terms.slug
FROM wp_posts
JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
JOIN wp_term_taxonomy ON wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
JOIN wp_terms ON wp_term_taxonomy.term_id = wp_terms.term_id
WHERE wp_posts.post_type = 'my-type'
   AND wp_posts.post_status = 'publish'
   AND wp_terms.slug IN
      ('field1', 'field2', 'field3')
   AND NOT wp_posts.id IN                # ADDED NOT
   (
      SELECT wp_postmeta.post_id
        FROM wp_postmeta
        WHERE wp_postmeta.meta_key = 'exclude' AND wp_postmeta.meta_value = '111'  #SINCE NOT ABOVE I CHANGED <> to =
           OR wp_postmeta.meta_key = 'include' AND wp_postmeta.meta_value <> '22'  #SINCE NOT ABOVE I CHANGED = to <>
           #I DELETED THIS LINE
   )

现在，如果未设置include或exclude，查询将返回数据。如果是，则检查ID。

对我的更改有何评论？

更多改进：

SELECT wp_posts.post_content, wp_posts.ID, wp_terms.slug
FROM wp_posts
JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
JOIN wp_term_taxonomy ON wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
JOIN wp_terms ON wp_term_taxonomy.term_id = wp_terms.term_id

WHERE wp_posts.post_type = 'my-type'
AND wp_posts.post_status = 'publish'
AND wp_terms.slug IN
('field1', 'field2', 'field3')

AND wp_posts.id NOT IN
(
SELECT wp_postmeta.post_id
FROM wp_postmeta

WHERE wp_postmeta.meta_key = 'exclude'
AND wp_postmeta.meta_value IN
('$id', '$id,%', '%,$id,%', '%,$id')

OR wp_postmeta.meta_key = 'include' 
AND wp_postmeta.meta_value NOT IN
('$id', '$id,%', '%,$id,%', '%,$id')

wp_postmeta表的示例：

Senario 1 - 只有身份标识为18的网页才能获取数据：

meta_id     post_id     meta_key    meta_value
1           30          include     18
2           30          _edit_lock  1322225789:1
3           30          _edit_last  1

Senario 2-id为18的页面无法获取数据：

meta_id     post_id     meta_key    meta_value
1           30          exclude     18
2           30          _edit_lock  1322225789:1
3           30          _edit_last  1

Senario 1 - 所有页面都应获取数据：

meta_id     post_id     meta_key    meta_value
2           30          _edit_lock  1322225789:1
3           30          _edit_last  1

Answer 1

我认为你根本不应该真正加入wp_postmeta，因为你实际上并不需要任何东西;相反，您应该使用IN或EXISTS子句执行“半连接”。例如：

SELECT wp_posts.post_content, wp_posts.ID, wp_terms.slug
FROM wp_posts
JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
JOIN wp_term_taxonomy ON wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
JOIN wp_terms ON wp_term_taxonomy.term_id = wp_terms.term_id
WHERE wp_posts.post_type = 'my-type'
   AND wp_posts.post_status = 'publish'
   AND wp_terms.slug IN
      ('field1', 'field2', 'field3')
   AND wp_posts.id IN
   (
      SELECT DISTINCT wp_postmeta.post_id
        FROM wp_postmeta
        WHERE wp_postmeta.meta_key = 'exclude' AND wp_postmeta.meta_value <> '111'
           OR wp_postmeta.meta_key = 'include' AND wp_postmeta.meta_value = '22'
           OR wp_postmeta.meta_key <> 'include' AND wp_postmeta.meta_key <> 'exclude'
   )

Answer 2

您可以使用子查询： http://dev.mysql.com/doc/refman/5.0/en/from-clause-subqueries.html

加入MySQL之前的聚合表（GROUP BY）

2 个答案: