我正在尝试创建单个查询以从主表(WordPress用户表)和用户元表中获取信息。
如果您不熟悉WP DB架构:wp_users保存基本用户信息及其ID,wp_usermeta包含ID,meta_key和meta_value。
假设我想让所有拥有某些meta_keys和meta_values的用户。这是我目前的查询(基于可用的meta_keys通过PHP生成):
SELECT ID,
user_email,
user_login,
first_name.meta_value as first_name,
last_name.meta_value as last_name,
phone_number.meta_value as phone_number,
wp_capabilities.meta_value as wp_capabilities
FROM wp_users,
(select * from wp_usermeta where meta_key = 'first_name') as first_name,
(select * from wp_usermeta where meta_key = 'last_name') as last_name,
(select * from wp_usermeta where meta_key = 'phone_number') as phone_number,
(select * from wp_usermeta where meta_key = 'wp_capabilities') as wp_capabilities
WHERE
ID = first_name.user_id AND
ID = last_name.user_id AND
ID = phone_number.user_id AND
ID = wp_capabilities.user_id AND
wp_wpi_capabilities.meta_value LIKE '%administrator%'
ORDER BY first_name
这样做很好,但是如果某个用户缺少meta_key,例如'last_name',则根本不会返回该用户行。所以我真正需要的是一种为缺少元键返回Null值的方法。
现在我有一个非常hackish的函数,它为所有没有给定meta_key的用户创建空白的meta_keys和meta_values,这样就可以返回它们。这是一种可怕的方式,但是当你拥有超过一千个用户时,你需要添加一种新类型的meta_key。
如果有人这样做,或者我需要更好地解释,请告诉我。
谢谢。
答案 0 :(得分:14)
将usermeta加入条件放在连接中,而不是苦苦于子查询:
SELECT
ID, user_email, user_login,
first_name.meta_value as first_name,
last_name.meta_value as last_name,
phone_number.meta_value as phone_number,
wp_capabilities.meta_value as wp_capabilities
FROM wp_users
JOIN wp_usermeta AS wp_capabilities ON wp_capabilities.user_id=ID
AND wp_capabilities.meta_key='wp_capabilities'
LEFT JOIN wp_usermeta AS first_name ON first_name.user_id=ID
AND first_name.meta_key='first_name'
LEFT JOIN wp_usermeta AS last_name ON last_name.user_id=ID
AND last_name.meta_key='last_name'
LEFT JOIN wp_usermeta AS phone_number ON phone_number.user_id=ID
AND phone_number.meta_key='phone_number'
WHERE
wp_capabilities.meta_value LIKE '%administrator%'
ORDER BY
first_name