public function unique_key_exists($value, $field)
	{
		$total = \DB::select(array(\DB::expr('COUNT(*)'), 'total_count'))
			->from($this->_table_name)
			->where($field, '=', $value)
			->where($this->_primary_key, '!=', $this->pk())
			->execute($this->_db)
			->get('total_count');

		return ($total == 0);
	}