From the above data, we need to write SQL commands to get the information from the following questions:

-Which student has taken the most classes?

-Which subject has been taken by the most students?

-For each student, what is their highest grade as a letter grade?

-How many students have taken classes in each subject?

-Which subject/s has had no students in it, if any?

-Are there any students who have taken no classes?

-Are there any grade ranges that have no student grades in them?

-List each subject and the student that has gotten the best grade in that subject as a letter grade.

-List each student, which subjects they have taken, and what the letter grade was for each of those subjects