Mysql Query返回0结果

Question

鉴于这两行中的值，为什么我的查询返回0行以及如何重写查询才能正常工作？

   SELECT * FROM wp_postmeta
    WHERE post_id = 73 
    AND ( meta_key = 'wpcf-mw' AND meta_value BETWEEN -8 AND 200 )
    AND ( meta_key = 'wpcf-milk' AND meta_value BETWEEN 20 AND 200 )

SQL查询：

{{1}}

Answer 1

id

通过OR更改AND。

Answer 2

基本上有两种方法可以做到这一点。一个大致如下：

SELECT post_id
     , MAX(CASE WHEN meta_key = 'wpcf-milk' THEN meta_value END) wpcf_milk
     , MAX(CASE WHEN meta_key = 'wpcf-mw' THEN meta_value END) wpcf_mw 
  FROM wp_postmeta 
 GROUP 
    BY post_id 
HAVING wpcf_milk BETWEEN 20 AND 200 
   AND wpcf_mw BETWEEN -8 AND 200;

另一种方法涉及OUTER JOIN并且速度稍快，但输入时稍微繁琐一点 - 所以我会留给其他人。