The dropDatabase command is used to drop a database. It also deletes the associated data files. It operates on the current database.
This syntax will delete the selected database. In the case you have not selected any database, it will delete default "test" database.
To check the database list, use the command show dbs:
If you want to delete the database "rookienerddb", use the dropDatabase() command as follows:
Now check the list of databases: