[RUBY] When registering a new user, I got an error called ActiveRecord :: NotNullViolation and how to deal with it.
Error in new user registration
I got the following error while implementing the user management function.
About white error
ActiveRecord::NotNullViolation in Devise::RegistrationsController#create
If you look it up on a reference site
"This error is an error caused by saving an item that should not be NULL due to DB constraints."
There was.
What I confirmed
① Migration file
In the image error statement above
Mysql2::Error: Field 'prefecture_address' doesn't have a default value
So I checked the migration file to confirm this.
Please see the image.
There seems to be no problem here because it is set like that in the migration file.
② Controller
If it is set in the migration file, I think that the recipient may not have received it, so next check the controller.
This was also the column name as specified in the migration file.
③ View
Now that I have migrated and controllered, I decided to check the view. (I'm a little impatient here.)
The image of the view is as follows. 
Did you understand ...
In the migration file and controller, it was prefecture_address, but in the view file, it was prefecture_address.
Code fix
When I finished modifying the view and made a new registration, I was able to register successfully.
Finally
Basically, when I get an error, I'm impatient with NoRoute Matches (I think I've overcome NoRoute Matches), so when I got an error I've never seen before, I thought, "Oh ... it's over ...". In this case, I didn't know which file the source code was referring to, so I wasn't rushed.
I was lucky to look into the error and hit the site. I will take this opportunity to add error tolerance. Excuse me.
References
【teratail】 Error when logging in / creating a new one by introducing the devise function https://teratail.com/questions/235508