The use command lets you access an existing database if you are a known user:
use database_name
For example, to access the pubs2 database, enter:
use pubs2
It is likely that you are automatically connected to the master database when you log in to Adaptive Server, so to use another database, issue the use command. You or a system administrator can change the database to which you initially connect by using sp_modifylogin. Only a system administrator can change the default database for another user.