Question

我正在尝试将Wordpress数据转换为我自己的数据库，他们的数据库结构给我带来了问题。这很难解释所以请耐心等待。

我有两张桌子如下。它们由wp_post.ID = wp_postmeta.post_id加入。

wp_posts
+----+------------+--------------+
| ID | post_title | post_content |
+----+------------+--------------+
| 1  | Game Title | some content |
+----+------------+--------------+

wp_postmeta
+---------+--------------+------------+
| post_id | meta_key     | meta_value |
+---------+--------------+------------+
|    1    | post_type    | Review     |
+---------+--------------+------------+
|    1    | game_rating  | 8.0        |
+---------+--------------+------------+
|    1    | game_genre   | FPS        |
+---------+--------------+------------+

现在我必须对我想要的每个meta_value条目（WHERE meta_value = 'Review'）进行查询。

我有办法运行单个查询并返回post_title，post_content，post_type，gaming_rating和game_genre吗？

Answer 1

看起来你需要在meta表上做几个自联接。

;with cte as(
  select pt.post_id, gr.meta_value as game_rating,
         gg.meta_value as game_genre
  from wp_postmeta pt
    inner join wp_postmeta gr
       on pt.post_id= gr.post_id and 
           gr.meta_key= 'game_rating'
    inner join wp_postmeta gg
   on pt.post_id = gg.post_id and 
       gg.meta_key = 'game_genre'
 where pt.meta_key ='post_type' and 
       pt.meta_value ='review'
 )
 select p.post_title, post_content,
        c.game_rating, c.game_genre
 from wp_post p
     inner join cte c
        on c.post_id = p.id

请参阅此小提琴http://sqlfiddle.com/#!3/e7559以查看其实际效果。

Answer 2

这是一种支点表;请参阅this question的答案，了解有关如何在MySQL中执行此操作的信息。

Answer 3

你可以做一个常规的内连接

SELECT post_id, post_title, post_content, meta_key, meta_value FROM wp_posts P INNER JOIN wp_postmeta PM ON (P.ID = PM.post_id) ORDER BY post_id

然后使用一个简单的脚本通过每个帖子的行进行迭代。我不知道你是否使用任何语言来访问数据库，但在python中（类似于伪代码：P）它将是这样的：

post = {}

for row in result:
   first_iteration = 'id' not in post

   if not first_iteration and row['post_id'] != post['id']:
      # we have a new post, process it.

   post['post_title'] = row['post_title']
   post['post_content'] = row['post_content']
   post[row[meta_key]] = row['meta_key']
   post['id'] = row['id']


 # process the last post

连接两个表，其中一个表有多行

3 个答案: