phpmysqlcodeignitermaxquery-builder

SELECT MAX() formatted string from a column using CodeIgniter's query builder

I want to select max auto_no from the following varchar type column in my CodeIgniter model

+------------+
|  auto_no   |
+------------+
| 2020-00821 |
| 2020-00822 |
| 2020-00823 |
| 2020-00824 |
| 2020-00825 |
+------------+

In this example that the value is 825. I tried following option

public function generate_auto_no($count = 1, $start = 00000, $digits = 5)
{
    $query = $this->db->get('letter_letter');
    $this->db->select("MAX(CAST(SUBSTRING_INDEX(auto_no, '-', -1) AS UNSIGNED)) AS auto_no", FALSE);        
    $count = ($query->num_rows() > 0) ? $query->row()->auto_no + 1 : 0;
    $result = array();
    for ($n = $start; $n <= $start + $count; $n++) {
        $result[] = str_pad($n, $digits, "0", STR_PAD_LEFT);
    }
    return date("Y").'-' . end($result);
}

But didn't get the expected value.

Solution

  • I thin you can just select the max string: 

    $this->db->select_max("auto_no");
$query = $this->db->get('letter_letter');
if ($query->num_rows() > 0) {
    $last_auto_no = $query->row()->auto_no;
    $no = intval(explode('-', $last_auto_no)[1]) + 1;
    $auto_no = date("Y").'-' . str_pad($no, $digits, "0", STR_PAD_LEFT);
} else {
    $auto_no = (date("Y").'-' . str_pad(0, $digits, "0", STR_PAD_LEFT));
}
return $auto_no