/**
  * Prepare column names for query
  *
  * @param array $columns
  * @return string
  */
 public static function columns(array $columns)
 {
     $columnValue = "";
     foreach ($columns as $key => $value) {
         if (is_numeric($key)) {
             $columnValue = "";
         } else {
             $columnValue = "{$key}.";
         }
         if (Steelcode_String_Helper::hasSubSting(' ', $value)) {
             $columnValue .= $value;
         } else {
             $columnValue = "`{$columnValue}{$value}`";
         }
         $columns[$key] = $columnValue;
     }
     return Steelcode_Array_Helper::implode(', ', $columns);
 }