The error is saying that the field branch_srl is null when it’s being inserted so it violates the NOT NULL CONSTRAINT. If you check your form, the form doesn’t use that field, but instead it uses branch_choices. You need to map the selected value for that field to branch_srl somewhere. It can be in TimetableForm.save(), AddTimetableView.form_valid() or you could rename the field branch_choices to branch_srl so it saves through to the database.