Unknown SQL Error! in SMSProv.log

I was at a customer who could not start ConfigMgr console on the site server after an CB update.
In SMSProv.log following messages was thrown:
*** *** Unknown SQL Error!
*~*~*** Unknown SQL Error!    ThreadID xxxx, DbError: 50000, Sev: 16~*~*
Results returned: 0 of -1

It turned out that the customer has performed a CB update. During the "Prerequisite Check" they had a warning on SQL server level.
After the update - that went well - they looked at the SQL server.
At some point someone has tried to install a service pack, which has only updated some (?) SQL components, leaving others in current state.
They tried to install the service pack again, but they could not, because the sql was already updated...
They detached the databases, uninstalled and installed the sql server, updated it and attached the databases again.

The ConfigMgr console could not start up...

I did the ConfigMgr Reset, checked the right on the SQL server and databases - all fine, but still the ConfigMgr console didn't start.

Luckily I found a post that stated that ConfigMgr requires SA to be owner of the database.
When you do an attach, the user doing this will become the owner.

I ran EXEC sp_helpdb and found the userid for the person who attached the databases as Owner.
To change the owner, I ran:
USE
GO
EXEC sp_changedbowner 'sa'

After this, I could start up the ConfigMgr console again.