The “input required” option of a field does not work in LibreOffice Base 7.3.5.2. No value is saved to the database even if the option is checked in the field properties.
I read that it was fixed in version 6.1.2.1, but it seems it does not work in 7.3.5.2.
Open the respective table for editing and make the respecitve table column mandatory. “Entry required”=Yes
Have reopened bug 75341. Seems it only has set fields in a form from “input required” → ‘yes’ to “input required” → ‘no’.
Better way will be to set it in datasource. Then the form will give (with “input required” → ‘yes’) in language of the user, not SQL.
Yup I can add this constraint to the table, but then what’s the point of the “input required” option?
It is very sad. You yourself had a discussion with someone in that bug, that the fix indeed forced people to change “required” to “no” to be able to not put data to respective fields, which definitely indicated that the respective fix was effective at that moment. And that means that any following regression is an own bug, and the general rule is “please do not reopen a bug that was closed fixed for a year or more”. Adding that bug to a “see also” of a new report is the proper way.
It is obsolete if you can do the same on database level. Sometimes you have no admin access to the connected database.
In fact, being able to set it on a control level could be useful when e.g. the requirement of a field data depends on data in other places, so some application logic can set/unset the option; or maybe could depend on a specific form (from several different forms used in different cases to put data to the same table).
No matter how desirable is the proper database design, the real life is a complex thing 
Created new: Bug 150577. As you wrote there: Seems to work right only for one week …
And here the solutions I wrote down in bug description:
We have three possibilities to solve this:
No. 3 would be the best solution.