Sum with join returns wrong data

I have 3 tables in the database and I'm trying to return summation from 2 columns regarding a criteria.

I need to list the sections [sec_name] , Defects QTY [sum(pdr_qty)] ,Production QTY [sum(pg_qty)]

Table1: sections

Table2: production_defects_report

Table3: production_gate

The Model

function fetch_data($limit, $start)
    {
        $today = date('Y-m-d');
        $this->db->select('sections.sec_name, SUM(production_defects_report.pdr_qty) as defect_qty, SUM(production_gate.pg_qty) as production_qty');
        $this->db->from('production_defects_report');
        $this->db->join('sections', 'sections.sec_id = production_defects_report.pdr_section_id');
        $this->db->join('production_gate', 'production_gate.pg_sec_id = production_defects_report.pdr_section_id ', 'left');
        $this->db->where('date(production_defects_report.pdr_date)',$today);
        $this->db->where('date(production_gate.pg_date)',$today);
        $this->db->group_by('sections.sec_id');
        $query = $this->db->get();


        if ($query->num_rows() > 0) {
            foreach ($query->result_array() as $row) {
                $data[] = $row;
            }

            return $data;
        }
        return false;
    }

I have created a Model function using codeignitor 3 but i found the summation result returned wrong in the other hand i recognized the result the summation duplicated and multiplies.

I think that when you JOIN with a table you multiply your rows, so joining with 2 tables would make too many rows to sum properly.

You can use a less efficient way, but one that works, by calculating each column using a sub-query. Don't forget to WHERE by the date.

SELECT 
    sec_name AS 'Section',
    (SELECT COALESCE(SUM(pdr_qty), 0) FROM production_defects_report AS pdr WHERE pdr.pdr_section_id = s.sec_id) AS 'Defects QTY',
    (SELECT COALESCE(SUM(pg_qty), 0) FROM production_gate AS pg WHERE pg.pg_sec_id = s.sec_id) AS 'Production QTY'
FROM 
    sections s;