將表加入自己和彼此

Question

我花了大部分時間試圖弄清楚這一點，所以我想是時候問專家了： 我試圖訪問WordPress以外的WordPress數據庫， m編寫查詢以從有點複雜的WordPress數據庫中獲取輸出。
數據庫中有幾個表使用meta_values和meta_keys將關於帖子或用戶的數據存儲在多行中。
例如，下面四個表，我需要從拉：

表：wp_postmeta

post_id | meta_key  | meta_value 
---------+-----------------+------------ 
2001  | _customer_user | 3 
2001  |order_description| smith 
2001  | _order_total | 300 

表：wp_posts

ID | post_type | post_status 
----+-----------+------------ 
2001| shop_order| publish 

表：wp_term_relationships

object_id | term_taxonomy_id 
----------+----------------- 
2001  | 190 

表： wp_usermeta

user_id | meta_key  |meta_value 
---------+-----------------+---------- 
    3  | first_name  | Andy 
    3  | last_name  | Mccormick 

我有了這個查詢工作的偉大，顯示訂單號（POST_ID）客戶ID，訂購介紹，和訂單總額在單行：在另一個領域我想

SELECT wp_posts.ID, wp_posts.post_title,ot.meta_value as total,od.meta_value as order_desc, cu.meta_value as customer     
     FROM wp_posts 
     LEFT JOIN wp_postmeta AS ot ON (wp_posts.ID = ot.post_id AND ot.meta_key='_order_total') 
     LEFT JOIN wp_postmeta AS od ON (wp_posts.ID = od.post_id AND od.meta_key='order_description') 
     LEFT JOIN wp_postmeta AS cu ON (wp_posts.ID =cu.post_id AND cu.meta_key='_customer_user') 
     LEFT JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id 
     WHERE wp_posts.post_type = 'shop_order' 
     AND wp_posts.post_status = 'publish' 
     AND wp_term_relationships.term_taxonomy_id = '190' 
     GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC" 

然而按名稱列出的客戶，而不是僅僅通過ID，所以我試圖從wp_usermeta表像這樣得到他們的第一個和最後一個名字：

SELECT wp_posts.ID, cu.meta_value as customer, fn.meta_vale as fname, ln.meta_value as lname     
       FROM wp_posts 
       LEFT JOIN wp_postmeta AS cu ON (wp_posts.ID = cu.post_id AND cu.meta_key='_customer_user') 
       LEFT JOIN wp_usermeta AS fn ON (cu.meta_key = fn.user_id AND fn.meta_key='first_name') 
       LEFT JOIN wp_usermeta AS ln ON (cu.meta_key = ln.user_id AND ln.meta_key='last_name') 
       LEFT JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id 
       WHERE wp_posts.post_type = 'shop_order' 
       AND wp_posts.post_status = 'publish' 
       AND wp_term_relationships.term_taxonomy_id = '190' 
       GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC; 

我也試過： LEFT JOIN wp_usermeta AS FN ON （（cu.me ta_key ='_ customer_user'）= fn.user_id AND fn.meta_key ='first_name'）以及大量的其他子查詢等等。

很明顯，我現在在SQL查詢中高於我的工資等級，所以任何幫助都會很棒。謝謝！

Answer 1

我不知道，不過你可以試試這個：

SELECT wp_posts.ID, cu.meta_value as customer, fn.meta_vale as fname, ln.meta_value as lname     
       FROM wp_posts 
       LEFT JOIN wp_postmeta AS cu ON (wp_posts.ID = cu.post_id AND cu.meta_key='_customer_user') 
       LEFT JOIN wp_usermeta AS fn ON (cu.meta_value = fn.user_id AND fn.meta_key='first_name') // Note meta_value instead of meta_key 
       LEFT JOIN wp_usermeta AS ln ON (cu.meta_value = ln.user_id AND ln.meta_key='last_name') // Note meta_value instead of meta_key 
       LEFT JOIN wp_term_relationships ON wp_posts.ID = wp_term_relationships.object_id 
       WHERE wp_posts.post_type = 'shop_order' 
       AND wp_posts.post_status = 'publish' 
       AND wp_term_relationships.term_taxonomy_id = '190' 
       GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC; 

從我想通了，cu.meta_value是在你的榜樣3，因爲它是用戶的ID，而cu.meta_key（如查詢）是'_customer_id'，因此您寧願要匹配cu.meta_value而不是cu.meta_key。雖然無法檢查，因爲我沒有WP安裝。