是否将.sql文件导入MySQL会覆盖现有数据库还是附加到它？

In some cases, I've had to do a mysqldump to produce a .sql file. After making some changes to the MySQL database for testing and development I want to restore it to the way it was before. So I import the .sql file. In the past I have delete the db and re-created it, and then did te import. Is that necessary? Does import from a .sql file overwrite and totally re-create the database and it's tables, or does it append to it? Thanks!In some cases, I've had to do a mysqldump to pr