2

我有一个带有下表的 WordPress 数据库

帖子

+--------------+
| Field        |
+--------------+
| ID           |
| post_author  |
| post_title   | 
| post_type    | 
+--------------+

后元

+--------------+
| Field        |
+--------------+
| meta_id      |
| post_id      |
| meta_key     |
| meta_value   |
+--------------+

并有记录meta_key值latitude和longitude

如何编写 SQL 来显示latitude并longitude作为结果列名？

+--------------+
| Field        |
+--------------+
| ID           |
| post_author  |
| post_title   |
| latitude     |
| longitude    | 
+--------------+

下面的查询是我的起点

SELECT ID, post_title, meta_key, meta_value FROM `wp_posts` 
LEFT JOIN `wp_postmeta` on ID=post_id 
WHERE post_type='place' AND (meta_key='latitude' OR meta_key='longitude') 
ORDER BY ID ASC
4

2 回答 2

3

听起来你想要and值PIVOT。不幸的是，MySQL 没有函数，但您可以使用带有语句的聚合函数来复制它：latitudelongitudePIVOTCASE

SELECT p.ID, 
  p.post_title, 
  p.post_author,
  max(case when pm.meta_key='latitude' then pm.meta_value end) latitude,
  max(case when pm.meta_key='longitude' then pm.meta_value end) longitude
FROM `wp_posts` p
LEFT JOIN `wp_postmeta` pm
  on p.ID=pm.post_id 
WHERE p.post_type='place' 
  AND (pm.meta_key='latitude' OR pm.meta_key='longitude') 
GROUP BY p.ID, p.post_title, p.post_author
ORDER BY p.ID ASC

请参阅带有演示的 SQL Fiddle

于 2012-11-06T11:27:49.427 回答
0

你可以使用这样的东西：

SELECT
  wp_posts.ID,
  wp_posts.post_title,
  wp_post_1.meta_value as latitude,
  wp_post_2.meta_value as longitude
FROM
  wp_posts
  LEFT JOIN wp_postmeta wp_post_1
  ON wp_posts.ID=wp_post_1.post_id and wp_post_1.meta_key = 'latitude'
  LEFT JOIN wp_postmeta wp_post_2
  ON wp_posts.ID=wp_post_2.post_id and wp_post_2.meta_key = 'longitude'
WHERE post_type='place'
ORDER BY ID ASC
于 2012-11-06T11:29:15.020 回答