We consider the table Teaching below. Check all statements that are True. We consider an ideal DBMS that would enforce all reactive constraints.

CREATE TABLE Teaching $($

ProfId INTEGER,

CrsCode CHAR $(6),$

Semester CHAR $(6),$

PRIMARY KEY $($CrsCode$,$ Semester$),$

FOREIGN KEY $($CrsCode$)$ REFERENCES Course,

FOREIGN KEY $($ProfId$)$ REFERENCES Professor $($Id$))$

Select $3$ correct answer$($s$)$

Question $9$ options:

A$-$ If we delete a professor in Professor, nothing happens in Teaching.

B$-$ If we update a semester in Teaching, nothing happens in Professor.

C$-$ If we delete a course $($CrsCode$)$ in Course, we delete the data about this course in Teaching.

D$-$ If we delete a course $($CrsCode$)$ in Course, we set to null the value of CrsCode in Teaching.