I have 2 table ('siswa' and 'pembayaran_spp')

I want to retrieve data from table pembayaran_spp by the biggest data of id_bulan.

My Model

function tunggakansppsiswa(){
  $this->db->select('siswa.*, tahun_masuk.keterangan_tahun_masuk, pembayaran_spp.id_bulan');
        $this->db->from('siswa');
        $this->db->join('tahun_masuk', 'tahun_masuk.id_tahun_masuk=siswa.id_tahun_masuk','left');
        $this->db->join('pembayaran_spp', 'pembayaran_spp.id_siswa=siswa.id_siswa','left');
        $this->db->group_by('siswa.id_siswa');
        $this->db->distinct();
        //$this->db->where()
        //$this->db->order_by('id_bulan',"desc");
        return $this->db->get();
}

done. thanks

$this->db->select('siswa.*, tahun_masuk.keterangan_tahun_masuk,pembayaran_spp.id_bulan');
        if ('pembayaran_spp.id_bulan = 0') {
            $this->db->select_max('pembayaran_spp.id_bulan');
    }

You can use $this->db->select_max("id_bulan"); or $this->db->select("id_bulan", false);