Support intro
Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 18.0.2)_: NextCloudPi 17.? to NextCloudPi 18.0.10
Operating system and version (eg, Ubuntu 20.04): Raspbian GNU/Linux 10 (buster)
Apache or nginx version (eg, Apache 2.4.25): ??
PHP version (eg, 7.1): PHP 7.3.19-1~deb10u1 (cli) (built: Jul 5 2020 06:46:45) ( NTS )
The issue you are facing:
I wanted to upgrade to 18.0.10 with the GUI. This gave the error:
InvalidArgumentException: Column name “oc_flow_operations”.“entity” is NotNull, but has empty string or null as default.
I know the sollution to that. I’ve got to edit the DB with MySQL. The only problem is i dont know what my username and password are for my DB. Is there a standard user or is there a way to recover the username/password or alter it?
Is this the first time you’ve seen this error? (Y/N): Y
The output of your Nextcloud log in Admin > Logging:
Update voorbereiden
Debug logniveau instellen
Onderhoudsmodus ingeschakeld
Herstel stap: Repair MySQL collation
Herstel informatie: All tables already have the correct collation -> nothing to do
Herstel stap: Repair SQLite autoincrement
Herstel stap: Copy data from accounts table when migrating from ownCloud
Herstel stap: Drop account terms table when migrating from ownCloud
Databaseschema aan het bijwerken
Database bijgewerkt
InvalidArgumentException: Column name "oc_flow_operations"."entity" is NotNull, but has empty string or null as default