My practice with h2 database and JavaFX to learn more about these technologies.
It is a simple window application that allows you to submit database queries using a form.
There are some SELECT, INSERT, UPDATE, and DELETE queries. You can add a row, edit it by editing the values in the form on the left side or delete a selected row.
5. subject "English" with rating 5 has been added and attempted to add a subject by the index that no one student has
(index_number in subjects is a FOREIGN key that references index_number in students, so in the students table there must be a student with a given index_number)
"Index not found!" is displayed in the first field
