Update the qualifying column value in a qualifying row without knowing the column name

I want to get a single row from db, remove one element from row and update that row back to db.

I wrote this code

$query = $this->db->get_where(TABLENAME, array('pin_code' => $pincode), 1);
          
$result = $query->result_array();
          
$array = $result[0]; 

if (($key = array_search($ccode, $array)) !== false) {
    unset($array[$key]);
} //$code is the value which i want to remove

$this->db->where('pin_code', $pincode);
$this->db->update(TABLENAME, $array); 

This is row

Array (
    [pin_code] => 854101
    [ccode_1] => 5806
    [ccode_2] => 
    [ccode_3] =>
    [ccode_4] =>
    [ccode_5] =>
    [ccode_6] =>
    [ccode_7] =>
    [ccode_8] =>
    [ccode_9] =>
    [ccode_10] =>
    [ccode_11] =>
    [ccode_12] =>
    [ccode_13] =>
    [ccode_14] =>
    [ccode_15] =>
    [ccode_16] =>
    [ccode_17] =>
    [ccode_18] =>
    [ccode_19] =>
    [ccode_20] =>
    [ccode_21] =>
    [ccode_22] =>
    [ccode_23] =>
    [ccode_24] =>
    [ccode_25] =>
    [ccode_26] =>
    [ccode_27] =>
    [ccode_28] =>
    [ccode_29] =>
    [ccode_30] =>
)

I just want to remove ccode_1 (this is not fixed depends upon $ccode value) value and update it back to db, but it's not showing desired result as above.

You don't need to unset the desired index just get that index and apply update

if (($key = array_search($ccode, $array)) !== false) {
$this->db->where('pin_code', $pincode);
$this->db->update(TABLENAME, array($key => ''));
}