我正在联接三个表，但我想将这些表之一的值分别用于其他两个表

Question

I have 3 Tables Questions, Answers and Comments where there are multiple answers to the same question and many comments to a single answer.

I want to show who answered the question and who commented to that answer.

As well i want to show the user who replied and users who commented on the same answer.

So please help me to join the same user table twice in both tables answers and comments.

Table: questions: id, text, user_id(fk)

Table: answers: id, que_id(fk), user_id(fk), text

Table: comments: id, ans_id(fk), user_id(fk), text

Table: users: id, name

$this->db->select('answers.id as aid,
                   answers.user_id as auser_id,
                   answers.text as atext,
                   comments.id as cid,
                   comments.user_id as cuser_id,
                   comments.text as ctext,
                   users.id as uid,
                   users.name as uname');
$this->db->from('answers');
$this->db->join('users','answers.user_id = users.id', 'left');
$this->db->join('ans_comments','answers.id = comments.ans_id', 'left');
$this->db->join('users','comments.user_id = users.id', 'left');
$this->db->where('que_id','1');
return $this->db->get();

My problem is that:

I am getting the same user for all comments.

I want different commentator for different comments.

Answer 1

If you are going to join the same table twice you should use a different name:

TESTED

$this->db->select('A.id AS A_id,
                   A.uid AS A_uid,
                   A.text AS A_text,
                   C.id AS C_id,
                   C.uid AS C_uid,
                   C.text AS C_text,
                   UA.id AS UA_id,
                   UA.name AS UA_name,
                   UC.id AS UC_id,
                   UC.name AS UC_name');
$this->db->from('answers AS A');
$this->db->join('comments AS C','C.aid = A.id', 'left');
$this->db->join('users AS UA','A.uid = UA.id', 'left');
$this->db->join('users AS UC','C.uid = UC.id', 'left');
$this->db->where('qid', 1);
$query = $this->db->get();

$result = $query->result_array();

If you noticed i used a different name for each join and used that name to get the related data, so if you want the user name for the answer you'd use UA.name and if you want it for the comment you'd user UC.name , and it gives you all the flexibility you need.