Database owner and permissions of the owner

Everything in database world must to have an owner. This is specially true regarding database itself. The owner of database has all available permissions in the database. Granting new permissions for database owner in the database does not make sense.

Changing the owner on database results in permissions to be changed, so usually if dba decides to change the ownership from LoginA to LoginB and LoginA should still have some a
ccess to the database, those permissions would need to be granted separately.

Let's suppose we have a database ALFA. We also have a server login AlfaApp. To create the login following command could be executed:

CREATE LOGIN AlfaApp WITH PASSWORD 's3cr3t5!'

To verify permissions of that user on the database try to start on behalf of the user USE statement:

[sap@localhost ~]$ isql -S192.168.2.11:5000 -UAlfaApp -Ps3cr3t5!
1> USE ALFA
2> GO
Msg 10351, Level 14, State 1:
Server 'SAP01', Line 1:
Server user id 6 is not a valid user in database 'ALFA'
1>

The error message is clear - user AlfaApp cannot access ALFA database. Who is the owner of database? This information can be displayed using sp_helpdb: