protected function individualColumnFilters()
    {
        $columnSearch = [];
        if (isset($this->individualColumnFiltering)) {
            $this->sRangeSeparator = isset($this->sRangeSeparator) ? $this->sRangeSeparator : '~';
            for ($i = 0, $ien = count($this->columns); $i<$ien; $i++) {
                if (self::isSearchable($this->columns[$i]) && !empty($this->request['columns'][$i]['search']['value'])) {
                    $search_value = trim($this->request['columns'][$i]['search']['value']);
                    $key = $this->toSQLColumn($this->columns[$i], 2, true);
                    $where_condition = $this->generateSQLColumnFilter($key, $search_value);
                    if (!$this->setHaving($where_condition, $this->columns[$i])) {
                        $columnSearch[] = $where_condition;
                    }
                }
            }
        }

        return implode(' AND ', $columnSearch);
    }