Codeigniter JOIN (SELECT query

Question

It is possible to generate the following query by CI Query Builder class ?

SELECT name 
       FROM table1 t1 
                   JOIN 
                              


        

Answer 1

this library can help you to use sub queries with query builder have look on the doc of this library

sub query with query builder

Answer 2

Well there are a couple of ways of doing it. One way is here which is a hack.

How can I rewrite this SQL into CodeIgniter's Active Records?

This other way is very simple.

$this->db
        ->select('ID')
        ->from('table2')
        ->order_by('id')
        ->limit('5');   

$subquery = $this->db->_compile_select();

$this->db->_reset_select(); 

$query  =       $this->db
                    ->select('t1.name')
                    ->from('table1 t1 ')
                    ->join("($subquery)  t2","t2.id = t1.t2_id")
                    ->get('table1 t1');

Some point about it.
You are bound to use from clause in subqueries because get runs the query.
In codeigniter 2 _compile_select and _reset_select can not be accessed because they are protected methods.
You may have to remove the keyword before both methods in system/database/DB_active_rec.php

This article is useful too.

Answer 3

in CI3, simply use the fourth parameters for escape

$this->db->from('table')
->join('SELECT id from table2 where something=%s) as T2'),'table.id=T2.id', 'LEFT',NULL)
->get()->row();

Don't forget to escape parameters in your subquery to avoid SQL Injection.