[英]Mysql Query returning 0 results
给定这两行中的值,为什么我的查询返回0行,如何重写查询才能正常工作?
meta_id post_id meta_key meta_value
1422 73 wpcf-milk 22
1423 73 wpcf-mw -7
SQL查询:
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 )
SELECT * FROM wp_postmeta
WHERE post_id = 73
AND (( meta_key = 'wpcf-mw' AND meta_value BETWEEN -8 AND 200 )
**OR** ( meta_key = 'wpcf-milk' AND meta_value BETWEEN 20 AND 200 ))
通过OR更改AND。
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些 - 所以我会把它留给其他人。
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