php - 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，它什么都不返回。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

以及不返回任何内容的查询:

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

更新 由于 OP 说 @bhelmet 发布了正确的答案，我想为 OP 澄清好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