Referential Integrity Constraints:

$(1)$ instructor$($dept$\_$name$)$department$($dept$\_$name$)$ on delete null.

$(2)$ teaches$($course$\_$id$,$ section$\_$id$,$ semester, year$)$ section$($course$\_$id$,$ section$\_$id$,$ semester, year$)$ on delete cascade.

$(3)$ teaches$($id$)$instructor$($id$)$ on delete cascade.

$(4)$ course$($dept$\_$name$)$ department$($dept$\_$name$)$ on delete set null.

$(5)$ section$($course$\_$id$)$course$($course$\_$id$)$ on delete cascade.

$(6)$ section$($building$,$room$\_$number$)$classroom$($building$,$ room$\_$number$)$ on delete set null.

$(7)$ student$($dept$\_$name$)$ department$($dept$\_$name$)$ on delete set null.

$(8)$ takes$($course$\_$id$,$ sec$\_$id$,$ semester, year$)$section$($course$\_$id$,$ sec$\_$id$,$ semester, year$)$ on delete cascade.

$(9)$ takes$($id$)$student$($id$)$ on delete cascade.

$(10)$ advisor$($i$\_$id$)$instructor$($id$)$ on delete set null.

$(11)$ advisor$($s$\_$id$)$ student$($id$)$ on delete cascade.

$(12)$ prereq$($course$\_$id$)$course$($course$\_$id$)$

$(13)$ prereq$($prereq$\_$id$)$ course$($course$\_$id$).$