'on子句'中的未知列'userc.u_id'(Unknown column 'userc.u_id' in 'on clause')

 我正在使用Codeigniter，我正在尝试使用所有已保存的自定义字段检索角色ID为3的所有用户。 出于某种原因，我收到了数据库错误 
 
 “ '条款'中的未知列'userc.u_id' ” 
 
   $this->db->join('(SELECT GROUP_CONCAT(data) AS custom_data, id AS dataid, u_id
     FROM ea_user_cfields userc
     GROUP BY id) AS tt', 'userc.u_id = ea.id','left');
    $this->db->join('(SELECT GROUP_CONCAT(name) AS custom_name, id AS customid
     FROM ea_customfields AS cf
     GROUP BY id) AS te', 'userc.c_id = cf.id','left');
    $this->db->where('id_roles', $customers_role_id);



    return $this->db->get('ea_users ea')->result_array();
 
 实际查询： 
 
SELECT * FROM (`ea_users` ea) 

LEFT JOIN (SELECT GROUP_CONCAT(data) AS custom_data, id AS dataid, u_id FROM
ea_user_cfields userc GROUP BY id) AS tt ON `userc`.`u_id` =
`ea`.`id` 

LEFT JOIN (SELECT GROUP_CONCAT(name) AS
custom_name, id AS customid FROM ea_customfields AS cf GROUP BY id) AS
te ON `userc`.`c_id` = `cf`.`id` WHERE `id_roles` = '3'

I am using Codeigniter and I am trying to retrieve all users with role ID 3 with all their saved custom fields. For some reason, I get a database error with
 
"Unknown column 'userc.u_id' in 'on clause'" 
 
   $this->db->join('(SELECT GROUP_CONCAT(data) AS custom_data, id AS dataid, u_id
     FROM ea_user_cfields userc
     GROUP BY id) AS tt', 'userc.u_id = ea.id','left');
    $this->db->join('(SELECT GROUP_CONCAT(name) AS custom_name, id AS customid
     FROM ea_customfields AS cf
     GROUP BY id) AS te', 'userc.c_id = cf.id','left');
    $this->db->where('id_roles', $customers_role_id);



    return $this->db->get('ea_users ea')->result_array();
 
Actual query:
 
SELECT * FROM (`ea_users` ea) 

LEFT JOIN (SELECT GROUP_CONCAT(data) AS custom_data, id AS dataid, u_id FROM
ea_user_cfields userc GROUP BY id) AS tt ON `userc`.`u_id` =
`ea`.`id` 

LEFT JOIN (SELECT GROUP_CONCAT(name) AS
custom_name, id AS customid FROM ea_customfields AS cf GROUP BY id) AS
te ON `userc`.`c_id` = `cf`.`id` WHERE `id_roles` = '3'

原文：https://stackoverflow.com/questions/39450909