Codeigniter joining tables? - php

Question

I have this structure of the tables:
Table Name: collisions
Fields: id, creator1, creator2
(1, 1, 2) - simple data in my sql table
Table Name: creators
Fields: id, artistname
(1, john smith)- simple data in my sql table
(2, steven michael)- simple data in my sql table
What i need is to join these tables so i can get the artist name instead of creator1 id and creator 2 id.
This is what I have done so far:
$this->db->select('collisions.*, creators.artist_name AS cr1, creators.artist_name as cr2');
$this->db->join('creators', 'collisions.creator1 = cr1.id AND collisions.creator2 = cr2.id', 'left');
$data = $this->db->get('collisions')->result();
but I am getting this error:
Unknown column 'cr1.id' in 'on clause'
SELECT `collisions`.*, `creators`.`artist_name` AS cr1, `creators`.`artist_name` as cr2 FROM (`collisions`) LEFT JOIN `creators` ON `collisions`.`creator1` = `cr1`.`id` AND collisions.creator2 = cr2.id
Can someone tell me what I am doing wrong?

Answer 1

This did the job
$this->db->select('collisions.*, cr1.artist_name as cr1, cr2.artist_name as cr2');
$this->db->join('creators AS cr1', 'collisions.creator1 = cr1.id', 'left');
$this->db->join('creators AS cr2', 'collisions.creator2 = cr2.id', 'left');
$data = $this->db->get('collisions')->result();

Answer 2

Please use actual table name instead of alias :
$this->db->select('collisions.*, creators.artist_name AS cr1, creators.artist_name as cr2');
$this->db->join('creators', 'collisions.creator1 = creators.id AND collisions.creator2 = creators.id', 'left');
$data = $this->db->get('collisions')->result();
the reason why you cant use alias is that the execution of sql is in the following order:
1)FROM clause
2)WHERE clause
3)GROUP BY clause
4)HAVING clause
5)SELECT clause
6)ORDER BY clause
since you were using alias which is created in select clause which executes after where clause.
That's why you can not use the alias that which does not exits.