Join tabel insert

public function testing()
{
    $builder = $this->db->table('tb_rt_report as rep');
    $builder->select("rep.rt_id, rep.g_id, rep.tg_name, rep.rt_prod_po, rep.rt_prod_id, rep.rt_prod_name, GROUP_CONCAT(rep.rt_prod_lot SEPARATOR ', ') AS rt_prod_lot, rep.rt_prod_delivery, sum(rep.rt_plan) as rt_plan, sum(rep.rt_actual) AS rt_actual, rep.sts_id ");
    $builder->where('rt_prod_delivery', '2023-10-27');
    $builder->groupBy('rep.rt_prod_id, rep.rt_prod_delivery');
    $rekap = $builder->get()->getResult();
    $row_rekap = $builder->get()->getNumRows();

    $inserted = 0;
    foreach($rekap as $rw)
    {
        if($rw->g_id == NULL)
        {
            $g_id = 2;
        }else{
            $g_id = $rw->g_id;
        }

        $g_id           = $g_id;
        $prod_id        = $rw->rt_prod_id;
        $prod_name      = $rw->rt_prod_name;
        $prod_lot       = $rw->rt_prod_lot;
        $prod_delivery  = $rw->rt_prod_delivery;
        $prod_plan      = $rw->rt_plan;
        $created_by     = $this->session->get('u_name');
        $created_date   = date('Y-m-d H:i:s');


        $query = $this->m_rekap->insert_rekap($g_id, $prod_id, $prod_name, $prod_lot, $prod_delivery, $prod_plan, $created_by, $created_date);

        $rk_id = $this->db->insertID();

        if($query)
        {
            $builder_group = $this->db->table('tb_group_details');
            $builder_group->select('*');
            $builder_group->where('g_id', $g_id);
            $result = $builder_group->get()->getResult();
            $row = $builder_group->get()->getNumRows();


            foreach($result as $k)
            {
                $rek_id = $rk_id;
                $pr_id  = $k->pr_id;
                $tg_name = 'Target-1';
                $sts_id = '3';
                $pr_id = $k->pr_id;

                $this->m_rekap->insert_details($rek_id, $pr_id, $tg_name, $sts_id);
            }

            $datas = [
                'rek_id' => $rek_id,
                'pr_id' => $pr_id,

            ];

            $inserted++;
        }
    }

    if($inserted > 0)
    {
        $rekap = $rk_id;
    }else{
        $rekap = "Gagal";
    }

    echo json_encode($rekap);
}