如何选择某些元键的所有元值？

Question

我正在尝试进行查询，但我无法掌握它。我想通过某些 meta_keys 选择所有记录。当我通过一个元键查询时它工作正常。但是当我想通过两个 meta_key 进行查询时，它什么也没有返回。有人可以帮帮我吗？！

有效的查询：

SELECT *
FROM `uszc_users` AS u, `uszc_utilizatori_acord` AS ua, `uszc_usermeta` AS ub
WHERE ua.email = u.user_email
AND ub.user_id = u.id
AND ub.meta_key = 'first_name'
AND acord = 'DA'
LIMIT 0 , 30

以及什么都不返回的查询：

SELECT *
FROM `uszc_users` AS u, `uszc_utilizatori_acord` AS ua, `uszc_usermeta` AS ub
WHERE ua.email = u.user_email
AND ub.user_id = u.id
AND ub.meta_key = 'first_name'
AND ub.meta_key = 'last_name'
AND acord = 'DA'
LIMIT 0 , 30

我有 3 个表，表 uszc_usermeta 包含 first_name 和 last_name，它们都在 meta_value 列中。

Answer 1

你不能有任何记录

AND ub.meta_key = 'first_name'
AND ub.meta_key = 'last_name'

没有意义，就这么简单：

SELECT *
FROM `uszc_users` AS u, `uszc_utilizatori_acord` AS ua, `uszc_usermeta` AS ub
WHERE ua.email = u.user_email
AND ub.user_id = u.id
AND (ub.meta_key = 'first_name'
OR ub.meta_key = 'last_name')
AND acord = 'DA'
LIMIT 0 , 30

UPDATE 由于 OP 说 @bhelmet 发布了正确答案，我想为 OP 澄清 good 查询应该如何看起来像恕我直言：

SELECT u.*, ub.meta_value first_name, uc.meta_value last_name
FROM `uszc_users` AS u  
INNER JOIN `uszc_utilizatori_acord` AS ua
ON ua.email = u.user_email
  AND ua.acord = 'DA'
INNER JOIN  `uszc_usermeta` AS ub
ON ub.user_id = u.id
  AND ub.meta_key = 'first_name'
INNER JOIN `uszc_usermeta` AS uc
ON uc.user_id = u.id
  AND uc.meta_key = 'last_name'
LIMIT 0 , 30

Answer 2

您要求提供meta_key 等于“first_name”和“last_name”的所有记录。你可能想做AND ub.meta_key IN ('first_name', 'last_name')之类的事情。

SELECT *
FROM `uszc_users` AS u, `uszc_utilizatori_acord` AS ua, `uszc_usermeta` AS ub
WHERE ua.email = u.user_email
AND ub.user_id = u.id
AND ub.meta_key IN ('first_name', 'last_name')
AND acord = 'DA'
LIMIT 0 , 30

Answer 3

要检查“usermeta”的两个条件，您应该加入表两次。你需要这样的东西：

SELECT *
FROM `uszc_users` AS u, `uszc_utilizatori_acord` AS ua, `uszc_usermeta` AS ub, `uszc_usermeta` AS uc
WHERE ua.email = u.user_email
AND ub.user_id = u.id
AND ub.meta_key = 'first_name'
AND uc.user_id = u.id
AND uc.meta_key = 'last_name'
AND acord = 'DA'
LIMIT 0 , 30