/**
  * Return a varchar type-formatted string
  *
  * @params array $values Contains a tokenised list of info about this data type
  * @return string
  */
 public function varchar($values)
 {
     $collation = MSSQLDatabase::get_collation();
     $collationSQL = $collation ? " COLLATE {$collation}" : "";
     return "nvarchar(" . $values['precision'] . "){$collationSQL} null";
 }