You can use either Sybase Central or a DROP DOMAIN statement to drop a domain.
Only a user with DBA authority or the user who created a domain can drop it. In addition, since a domain cannot be dropped if any variable or column in the database uses the domain, you need to first drop any columns or variables of that type before you can drop the domain.
Open the Domains folder.
Click the desired domain and choose Edit > Delete.
Connect to a database.
Execute a DROP DOMAIN statement.
The following statement drops the persons_name domain.
DROP DOMAIN persons_name;
For more information, see DROP statement.