Question

查询就是这个：

    SELECT resume.user_id
    FROM ".$wpdb->prefix."wpjb_meta as meta
    JOIN ".$wpdb->prefix."wpjb_meta_value as value_von
    ON meta.id = value_von.meta_id AND meta.meta_object = 'resume' AND meta.name = 'arbeitsregion_von'
    JOIN ".$wpdb->prefix."wpjb_meta_value as value_bis
    ON meta.id = value_bis.meta_id AND meta.meta_object = 'resume' AND meta.name = 'arbeitsregion_bis'          
    JOIN ".$wpdb->prefix."wpjb_resume as resume
    ON value_bis.object_id = resume.id
WHERE value_von.value <= 222222 AND value_bis.value >= 222222

我的问题是第二次加入：它再次加入同一个表，添加一个内容为“arbeitsregion_bis”的列。结果应该是这样的：

resume.user_id
-------4-------
-------6-------

但是查询的结果总是没有条目。为什么呢？

编辑：我不需要这些值，我只需要在WHERE条件下的那些，sry。

Answer 1

通过你正在进行的连接，你假设meta.name同时有两个值，'arbeitsregion_von'和'arbeitsregion_bis'，这是不可能的。

此查询应该为您提供所需的内容（每个用户只有两行）。

SELECT resume.user_id, meta.name as von_bis, my_values.value
FROM ".$wpdb->prefix."wpjb_meta as meta
JOIN ".$wpdb->prefix."wpjb_meta_value as my_values
ON meta.id = my_values.meta_id AND meta.meta_object = 'resume'
JOIN ".$wpdb->prefix."wpjb_resume as resume
ON my_values.object_id = resume.id
WHERE
meta.name IN ('arbeitsregion_von', 'arbeitsregion_bis')

要将它放在一列中，您必须转动：

SELECT resume.user_id, 
MAX(CASE WHEN meta.name = 'arbeitsregion_von' THEN my_values.value END) AS von,
MAX(CASE WHEN meta.name = 'arbeitsregion_bis' THEN my_values.value END) AS bis
FROM ".$wpdb->prefix."wpjb_meta as meta
JOIN ".$wpdb->prefix."wpjb_meta_value as my_values
ON meta.id = my_values.meta_id AND meta.meta_object = 'resume'
JOIN ".$wpdb->prefix."wpjb_resume as resume
ON my_values.object_id = resume.id
WHERE
meta.name IN ('arbeitsregion_von', 'arbeitsregion_bis')
GROUP BY resume.user_id

编辑：为了满足您的新要求，最简单的方法

SELECT resume.user_id, 
MAX(CASE WHEN meta.name = 'arbeitsregion_von' THEN my_values.value END) AS von,
MAX(CASE WHEN meta.name = 'arbeitsregion_bis' THEN my_values.value END) AS bis
FROM ".$wpdb->prefix."wpjb_meta as meta
JOIN ".$wpdb->prefix."wpjb_meta_value as my_values
ON meta.id = my_values.meta_id AND meta.meta_object = 'resume'
JOIN ".$wpdb->prefix."wpjb_resume as resume
ON my_values.object_id = resume.id
WHERE
meta.name IN ('arbeitsregion_von', 'arbeitsregion_bis')
GROUP BY resume.user_id
HAVING von <= 222222  AND bis >= 222222

自我加入SQL无法正常工作

1 个答案: