i have a db collection "feedbacks" with 2 fieds. filed 1- id of the student, filed 2 - feedback description.
i want to prevent cases that user insert to the db identical description feedbacks to certain student.
for example, id student "123" has description feedback "very good"
and another diffrents descriptions like "need to improve at..." and more....
but if the user try to insert again to student "123" the feedback description "very good", the system display error.
how can i do this?