Question

I have the following mysql query. Could you please tell me how to write the same query in Codeigniter’s way ?

SELECT * FROM myTable 
         WHERE trans_id IN ( SELECT trans_id FROM myTable WHERE code='B') 
         AND code!='B'

Answer 1

You can use sub query way of codeigniter to do this for this purpose you will have to hack codeigniter. like this
Go to system/database/DB_active_rec.php
Remove public or protected keyword from these functions

public function _compile_select($select_override = FALSE)
public function _reset_select()

Now subquery writing in available
And now here is your query with active record

$this->db->select('trans_id');
$this->db->from('myTable');
$this->db->where('code','B');
$subQuery = $this->db->_compile_select();

$this->db->_reset_select();
// And now your main query
$this->db->select("*");
$this->db->where_in("$subQuery");
$this->db->where('code !=', 'B');
$this->db->get('myTable');

And the thing is done. Cheers!!!
Note : While using sub queries you must use

$this->db->from('myTable')

instead of

$this->db->get('myTable')

which runs the query.
Watch this too

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

Note : In Codeigntier 3 these functions are already public so you do not need to hack them.