How to change SQL format - php

Question

I have an SQL Query like this
return $this->db->query("SELECT * FROM `rincian_permintaan`
JOIN `permintaan` ON `permintaan`.`id_permintaan` = `rincian_permintaan`.`id_permintaan`
JOIN `users` ON `permintaan`.`id_peminta` = `users`.`user_id`
JOIN `cabang` ON `cabang`.`id_cabang` = `users`.`id_cabang`
JOIN `barang` ON `barang`.`id_barang` = `rincian_permintaan`.`id_barang`
JOIN `po` ON `rincian_permintaan`.`id_po` = `po`.`id_po` WHERE `po`.`id_cabang` = '201' AND `users`.`id_cabang` != 201 AND
NOT EXISTS(SELECT * FROM airwaybill WHERE airwaybill.id_rincian_permintaan = rincian_permintaan.id_rincian_permintaan)
ORDER BY rincian_permintaan.created_at DESC")->result_array();
I want to change the format to:
$this->db->select('*');
$this->db->from('tableName');
$this->db->join('...');
$this->db->where('...');
And this is what i've tried:
$this->db->select('*');
$this->db->from('rincian_permintaan');
$this->db->join('permintaan', 'permintaan.id_permintaan = rincian_permintaan.id_permintaan');
$this->db->join('users', 'permintaan.id_peminta = users.user_id');
$this->db->join('cabang', 'cabang.id_cabang = users.id_cabang');
$this->db->join('barang', 'barang.id_barang = rincian_permintaan.id_barang');
$this->db->join('po', 'rincian_permintaan.id_po = po.id_po');
$this->db->where('po.id_cabang', '201');
$this->db->where('users.id_cabang != 201');
$this->db->select('*');
$this->db->from('airwaybill');
$this->db->where('NOT EXISTS airwaybill.id_rincian_permintaan = rincian_permintaan.id_rincian_permintaan', '', FALSE);
return $this->db->get('rincian_permintaan')->result_array();
Error:

Answer 1

All you need is to generate sql string for subquery without executing it and use it in the outer query and produce the result.
$this->db->select('*');
$this->db->from('airwaybill');
$this->db->where('airwaybill.id_rincian_permintaan = rincian_permintaan.id_rincian_permintaan');
$sub_query = $this->db->get_compiled_select();
$this->db->select('*');
$this->db->from('rincian_permintaan');
$this->db->join('permintaan', 'permintaan.id_permintaan = rincian_permintaan.id_permintaan');
$this->db->join('users', 'permintaan.id_peminta = users.user_id');
$this->db->join('cabang', 'cabang.id_cabang = users.id_cabang');
$this->db->join('barang', 'barang.id_barang = rincian_permintaan.id_barang');
$this->db->join('po', 'rincian_permintaan.id_po = po.id_po');
$this->db->where('po.id_cabang', '201');
$this->db->where('users.id_cabang != 201 ');
$this->db->where('NOT EXISTS('.$sub_query.')');
$query = $this->db->get();
$result = $query->result_array();
return $result;