我需要一个meta_value 来自wp\\U Posteta，我可以使用一个类别，但使用另一个类别时遇到问题。

我有：

SELECT wp_posts.ID, wp_postmeta.meta_value FROM wp_postmeta
LEFT JOIN wp_posts ON wp_posts.ID = wp_postmeta.post_id
LEFT JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
LEFT JOIN wp_term_taxonomy ON wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
WHERE wp_postmeta.meta_key = \'_application\'
AND wp_term_taxonomy.term_id = \'14\'

我的结果是：

ID | meta_value
91 | [email protected]
99 | [email protected]

当我更改最后一行时wp_term_taxonomy.term_id = \'14\' 到wp_term_taxonomy.term_id = \'31\' 我将获得：

ID | meta_value
91 | [email protected]
95 | [email protected]

当我使用2个类别时，问题开始出现

SELECT wp_posts.ID, wp_postmeta.meta_value FROM wp_postmeta
LEFT JOIN wp_posts ON wp_posts.ID = wp_postmeta.post_id
LEFT JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id
LEFT JOIN wp_term_taxonomy ON wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
WHERE wp_postmeta.meta_key = \'_application\'
AND wp_term_taxonomy.term_id = \'14\'
AND wp_term_taxonomy.term_id = \'31\'

那我什么也得不到

MySQL返回一个空结果集（即零行）。

我应该得到：

ID | meta_value
91 | [email protected]

如何使用这两个类别(term_id = \'14\' 和term_id = \'31\' ) 同时在一个查询中，这样我的结果将只显示两个类别中的帖子的meta\\u值？

SELECT wp_posts.ID, wp_postmeta.meta_value FROM wp_postmeta    
INNER JOIN wp_posts ON wp_posts.ID = wp_postmeta.post_id
INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id)  
INNER JOIN wp_term_relationships AS tt1 ON (wp_posts.ID = tt1.object_id) 
WHERE 1=1 
AND wp_postmeta.meta_key = \'_application\'
AND ( wp_term_relationships.term_taxonomy_id IN (31) 
  AND 
  tt1.term_taxonomy_id IN (14)
)