code: private function appendDesc(&$column): void
  	{
  		if (is_array($column)) 
  		{
  			foreach ($column as &$col) 
  			{
  				$col = "$col DESC";
  			}
  		}
  		else 
  		{
  			$column = ["$column DESC"];
  		}
  	}
docs: Append the DESC keyword to all requested keywords or expressions.
  @param string|array $column