To backup and restore a MySQL database with all tables from a command prompt:
To Backup the database:
mysqldump -u username -ppassword database_name > dump.sql
To Restore the file:
mysql -u username -ppassword database_name < dump.sql
Here's a Great Document explaining the process in more detail:
http://www.mydigitallife.info/2007/07/21/how-to-backup-and-restore-export-and-import-mysql-databases-tutorial/