mysql - SQL - 如何连接这个表？

Question

通过运行这个 SELECT 查询:

SELECT wp_posts.ID, wp_postmeta.meta_key, wp_postmeta.meta_value
FROM wp_posts
INNER JOIN wp_postmeta
ON wp_posts.ID = wp_postmeta.post_id
WHERE wp_posts.post_status = 'publish' 
AND wp_posts.post_type = 'my_post_type'
AND wp_posts.post_date < NOW()
AND wp_postmeta.meta_key = 'wpcf-lat'
OR wp_postmeta.meta_key = 'wpcf-long'

我得到这样的表格:

id     meta_key     meta_value
------------------------------
1270   wpcf-lat     12.6589
1270   wpcf-long    78.7425
1658   wpcf-lat     22.3654
1658   wpcf-long    65.2985

但是我需要这样的结果表

id     wpcf-lat     wpcf-long
------------------------------
1270   12.6589      78.7425
1658   22.3654      65.2985

我怎样才能做到这一点？

Answer 1

对于一组已知的meta_key，您可以使用以下查询

select 
wp.ID, 
max(
   case when pm.meta_key = 'wpcf-lat' then pm.meta_value end
) as `meta_value`,
max(
  case when pm.meta_key = 'wpcf-long' then pm.meta_value end
) as `wpcf-long` 
from wp_posts wp 
join  wp_postmeta pm on pm.post_id = wp.ID 
group by  wp.ID ;