本文介绍了如果列值不存在,则不要加入表的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
SELECT
`wp_emu_theme_contact_page`.`firstName`
, `wp_emu_theme_contact_page`.`city`
, `wp_emu_theme_contact_page`.`state`
, `wp_posts`.`post_content`
, `wp_posts`.`post_date`
, `wp_posts`.`post_type`
, `wp_posts`.`ID`
, `wp_emu_theme_testimonials`.`permission`
, `wp_emu_theme_testimonials`.`userID`
, `wp_users`.`user_login`
, `wp_usermeta`.`meta_value`
FROM
`wp_emu_theme_testimonials`
INNER JOIN `wp_emu_theme_contact_page`
ON (`wp_emu_theme_testimonials`.`contactID` = `wp_emu_theme_contact_page`.`dbID`)
INNER JOIN `wp_posts`
ON (`wp_emu_theme_testimonials`.`postID` = `wp_posts`.`ID`)
LEFT JOIN `wp_users`
ON (`wp_emu_theme_testimonials`.`userID` = `wp_users`.`ID`)
INNER JOIN `wp_usermeta`
ON (`wp_usermeta`.`user_id` = `wp_users`.`ID`)
WHERE (`wp_posts`.`post_type` ='testimonial'
AND `wp_usermeta`.`meta_key` ='facebook_uid')
OR (`wp_usermeta`.`meta_key` = 'null');
问题是表 wp_usermeta 可能没有 meta_key = 'facebook_uid'.在这种情况下,我没有收到这些条目.我想获得所有其他东西,即使那个 user_id 不存在 meta_key.如果是这样,那就太好了.如果我取出有关该表的部分,此查询将按预期工作.我试过没有手术室.我用的是mysql.
The problem is that table wp_usermeta might not have a meta_key = 'facebook_uid'. In that case, I am not getting those entries. I want to get all the other stuff, even if that meta_key doesnt exist for that user_id. And if it does, great. This query works as expected if I take out the parts regarding that table. I've tried without the OR. I am using mysql.
推荐答案听起来您想使用 LEFT JOIN 并使 ON 的条件部分成为:
It sounds like you want to use LEFT JOIN and make that conditional part of the ON:
LEFT JOIN `wp_usermeta` ON (`wp_usermeta`.`user_id` = `wp_users`.`ID` AND `wp_usermeta`.`meta_key` ='facebook_uid')更多推荐
如果列值不存在,则不要加入表
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