How to join the same table twice and assign table aliases in Codeigniter?

Question

I'm trying to make a mail system in Codeigniter with the PyroCms. In my mail table, I have a "recipent" row and a "sender" row which contains the user id of the sender and recipient. To retrieve usernames from the ids, I'm trying to join the table together, but it simply returns me this error:

Error Number: 1066

Not unique table/alias: 'default_users'

SELECT `default_mailsystem`.*, `default_users`.`username` AS modtager, `default_users`.`username` as afsender
FROM (`default_mailsystem`)
LEFT JOIN `default_users` ON `default_mailsystem`.`recipent` = `default_modtager`.`id`
LEFT JOIN `default_users` ON `default_mailsystem`.`sender` = `default_afsender`.`id`
ORDER BY `id` DESC

Filename: /hsphere/local/home/brightmedia/reuseable.dk/modules/mail/models/mail_m.php

Line Number: 13

My code is as follows:

$this->db->select('mailsystem.*, users.username AS modtager, users.username as afsender')
    ->join('users', 'mailsystem.recipent = modtager.id', 'left')
    ->join('users', 'mailsystem.sender = afsender.id', 'left');
$this->db->order_by('id', 'DESC');
return $this->db->get('mailsystem')->result();

The funny thing is, that if I remove the last "join" operation and leave it to only join the recipient of the mail it all works out well.

Thylacine

@mickmackusa As requested, now renewed. – Thylacine

Answer 1

At the time of this thread, i figured that the codeigniter call missed out the possibility to do AS inside of a join, Therefor this solved the issue:

$sql = "
    SELECT default_mailsystem.*,
           recipent.first_name AS modtager, 
           sender.first_name AS afsender
    FROM default_mailsystem
    LEFT JOIN default_profiles AS recipent ON recipent.id = default_mailsystem.id
    LEFT JOIN default_profiles AS sender ON sender.id = default_mailsystem.id
";
return $this->db->query($sql)->result();

Thylacine

This answer is not enjoying CI's query building methods. – Nutation

Answer 2

This is very simple

$this->db->select('mailsystem.*, users.username AS modtager, users.username as afsender')
$this->db->join('users', 'mailsystem.recipent = modtager.id AND mailsystem.sender = afsender.id', 'left')
$this->db->order_by('id', 'DESC');
return $this->db->get('mailsystem')->result();

Rebekahrebekkah

This code-only answer changes the query logic. This answer will be misleading researchers that want to join the same table twice to the first table. – Nutation

Answer 3

Have you tried forcing an alias in the join function (the "AS" operator won't work in the select clause as you have it...)?

<?php
$this->db->select('mailsystem.*, modtager.username AS modtager_name, afsender.username as afsender_name')
    ->join('`users` `modtager`', 'mailsystem.recipent = modtager.id', 'left')
    ->join('`users` `afsender`', 'mailsystem.sender = afsender.id', 'left');

$this->db->order_by('mailsystem.id', 'DESC');

return $this->db->get('mailsystem')->result();

Engel

Manually adding backticks defies the feature of ActiveRecord methods providing identifier escaping for you (that will still hold up when moving to a different database). In other words, the idea of using the query builder methods is so that you don't need to manually quote parts of your query. – Nutation

Answer 4

Use alias like this -

$this->db->select('mailsystem.*, users_table_a.username AS modtager, users_table_b.username as afsender')
$this->db->join('users users_table_a', 'mailsystem.recipent = users_table_a.id', 'left');
$this->db->join('users users_table_b', 'mailsystem.sender = users_table_b.id', 'left');
$this->db->order_by('id', 'DESC');
return $this->db->get('mailsystem')->result();

Wunder

This answer is missing its explanation. This "block of code" answer will require researchers to scroll and scrutinize the OP's code with your code. – Nutation

Answer 5

you can use this :

$this->db->select('mailsystem.*, users.username AS modtager, users.username as afsender')
$this->db->join('users', 'mailsystem.recipent = modtager.id AND mailsystem.sender = afsender.id', 'left')
$this->db->order_by('id', 'DESC');
return $this->db->get('mailsystem')->result();

*If you are using any db prefix use this *

$this->db->select('mailsystem.*, users.username AS modtager, users.username as afsender')
$this->db->join('users', 'mailsystem.recipent = modtager.id AND '.$this->db->dbprefix('mailsystem').'.sender = '.$this->db->dbprefix('afsender').'.id', 'left')
$this->db->order_by('id', 'DESC');
return $this->db->get('mailsystem')->result();

Joggle

This "use this" (no explanation) answer is not joining the same table to the parent table twice -- it is joining a table to the parent table once. – Nutation

Answer 6

Its very easy to get data from single table
$this->db->select('a.*,b.fname AS cname,c.fname as uname'); 
$this->db->from('tbl_menus a'); 
$this->db->join('tbl_admin_login b', 'b.id = a.create_by', 'left'); 
$this->db->join('tbl_admin_login c', 'c.id = a.update_by', 'left'); 
$this->db->order_by('a.id', 'desc'); 
return $this->db->get()->result_array();

Magus

While this code may solve the question, including an explanation of how and why this solves the problem would really help to improve the quality of your post, and probably result in more up-votes. Remember that you are answering the question for readers in the future, not just the person asking now. Please edit your answer to add explanations and give an indication of what limitations and assumptions apply. – Overture

This answer makes no attempt to dignify the OP's data/values. It looks more like this code-only answer is answering a different question that requires the same technique. – Nutation

Answer 7

Your can try this Core PHP

SELECT `custome_module`.`id`, `custome_module`.`name`, min(l1.nmark_completed) as call_waiter, min(l2.nmark_completed) as bill, min(l3.nmark_completed) as tray, min(l4.nmark_completed) as ordera
FROM `custome_module`
LEFT JOIN `restaurant_logs` as `l1` ON `custome_module`.`id` = `l1`.`nmodule_id` AND `l1`.`ntype` = 1
LEFT JOIN `restaurant_logs` as `l2` ON `custome_module`.`id` = `l2`.`nmodule_id` AND `l2`.`ntype` = 2
LEFT JOIN `restaurant_logs` as `l3` ON `custome_module`.`id` = `l3`.`nmodule_id` AND `l3`.`ntype` = 6
LEFT JOIN `restaurant_logs` as `l4` ON `custome_module`.`id` = `l4`.`nmodule_id` AND `l4`.`ntype` = 5
WHERE `custome_module`.`nbranch_id` = '142'
GROUP BY `custome_module`.`id`

and also in Codeigniter

$this->db->select('custome_module.id, custome_module.name, min(l1.nmark_completed) as call_waiter, min(l2.nmark_completed) as bill,min(l3.nmark_completed) as tray,min(l4.nmark_completed) as ordera');
$this->db->from("custome_module");
$this->db->join('restaurant_logs as l1', 'custome_module.id = l1.nmodule_id AND l1.ntype = 1', 'left');
$this->db->join('restaurant_logs as l2', 'custome_module.id = l2.nmodule_id AND l2.ntype = 2', 'left');
$this->db->join('restaurant_logs as l3', 'custome_module.id = l3.nmodule_id AND l3.ntype = 6', 'left');
$this->db->join('restaurant_logs as l4', 'custome_module.id = l4.nmodule_id AND l4.ntype = 5', 'left');
$this->db->where('custome_module.nbranch_id', $this->data['user_session']['nid']);
$this->db->get();

Ensanguine