MySQL JOIN 和 WHERE - 我的查询出了什么问题

Question

我正在尝试从我的两个表中获取一些用户数据。知道出了什么问题吗？如有任何帮助，我们将不胜感激。

Error message:

Unknown column 'a3p_user_fields.user_id' i tabel field list

我的表格:

**a3p_user_fields**

user_id, 
field_title, 
field_job_title, 
field_education, 
field_experience, 
field_hourly_wage, 
field_support, 
field_fee, 
field_description,

**a3p_usermeta**

umeta_id, 
user_id, 
meta_key, 
meta_value

我的查询:

    SELECT `a3p_user_fields.user_id`, `a3p_user_fields.field_job_title`, 
   `a3p_user_fields.field_education`, `a3p_user_fields.field_experience`, 
   `a3p_user_fields.field_hourly_wage`, `a3p_usermeta.meta_key` FROM 
   `a3p_user_fields` INNER JOIN `a3p_usermeta` 
   ON `a3p_user_fields.user_id` = 'a3p_usermeta.user_id` 
   WHERE `a3p_user_fields.field_title` = 'Gartner' 
   AND `a3p_usermeta.meta_key` = 'candidate_flexjob' AND `a3p_usermeta.metavalue` = 'Ja' 
  ORDER BY `a3p_user_fields.user_id` ASC

Answer 1

问题出在下面几行，我认为这是一个引用问题

ON `a3p_user_fields.user_id` = 'a3p_usermeta.user_id`

你是这么想的

ON `a3p_user_fields`.`user_id` = `a3p_usermeta`.`user_id`

您选择列的方式也不正确，例如

SELECT `a3p_user_fields.user_id`

您应该分别引用表名和列名

SELECT `a3p_user_fields`.`user_id`