added some bullshit, but motivation about -9 and there's a bunch to go

a2/a2.sql

@@ -1,4 +1,11 @@
-select sname, snum from student where year = 2 and snum in
+-- Current term is 1185
+
+/*
+The student number and name of second year students who have obtained
+a grade lower than 65 in at least two courses in a department with the
+name “computer science”.
+*/
+select distinct sname, snum from student where year = 2 and snum in
 (
   select snum from mark where grade < 65 and deptcode in
   (
@@ -6,7 +13,11 @@ select sname, snum from student where year = 2 and snum in
   ) having count(distinct section) > 1
 )
 
-select pnum, pname from professor where deptcode not in
+/*
+The number and name of professors who are not in the pure math (PM)
+department, and who are teaching CS245 for the first time.
+*/
+select distinct pnum, pname from professor where deptcode not in
 (
   select deptcode fromm department where deptname = "PM"
 ) and pnum in
@@ -14,3 +25,99 @@ select pnum, pname from professor where deptcode not in
   select pnum from class where deptcode = "CS" and cnum = 245
 ) having count(distinct term) = 1
 
+/*
+The number, name and year of each student who has obtained a grade in
+CS240 that is within 3 marks of the highest ever grade recorded for that
+course.
+*/
+select distinct snum, sname, year from student where snum in
+(
+  select snum, grade from mark where deptcode = "CS" and cnum = 240 and snum >= (select max(grade) from mark where deptcode = "CS" and cnum = 240)
+)
+
+/*
+ The number and name of students who have completed two years, who
+have a final grade of at least 85 in every computer science course that
+they have taken, and who have always been taught by a professor in the
+computer science (CS) department.
+ASSUMING THIS PROFESSOR RESTRICTION ONLY APPLIES TO THE CS COURSES
+*/
+select distinct snum, sname from student where year > 2 and snum not in
+(
+  select snum, grade from mark where deptcode = "CS" and grade < 85
+) and snum not in
+(
+  select snum as prev_snum, deptcode as prev_deptcode, cnum as prev_cnum, term as prev_term, section as prev_section from mark where cnum in
+  (
+    select pnum, cnum from class where prev_deptcode = deptcode and prev_cnum = cnum and prev_term = term and prev_section = section and pnum in
+    (
+      select pnum from professor where deptcode = prev_deptcode
+    )
+  )
+)
+
+/*
+ A sorted list of all departments who do not have a professor currently
+teaching a course offered by a different department.
+*/
+select deptname as prof_dept from department where deptcode not in
+(
+  select deptcode as old_dept, pnum as old_pnum from professor where pnum in
+  (
+    select pnum from class where term = 1185 and deptcode != old_dept and pnum = old_pnum
+  )
+) order by deptname
+
+/*
+For each pair of classes for the same course that were taught in the same
+term, and that where also taught by different professors: the minimum
+grades obtained and the maximum grades obtained. In addition to these
+four values, each result should include the number and name of each professor,
+as well as the identifying attributes for each class.
+*/
+
+/*
+Pairs of distinct professors such that whenever the first one teaches a class
+in a particular term the second also teaches a class for the same course
+in the same term. Report a oprofessor number and name for both the
+professors.
+*/
+
+-- NOW CAN USE AGGREGATION
+
+/*
+The course number and total enrollment count for all of its classes of each
+course. Also, include only those course numbers for courses with a total
+enrollment count among the three lowest such counts.
+*/
+
+/*
+The percentage of professors in pure math who have always taught no
+more than a single course in any given term. (Note that a percentage
+should be a number between 0 and 100.)
+*/
+
+/*
+The number of different third or fourth year students in each section of
+each course taught by a pure math professor in past terms. The result
+should include the professor number, professor name, course number and
+section, and should also be sorted first by the name of the professor,
+then by the professor number, third by the course number, and finally by
+section. (Note that a section is identified by a term and a section number.
+Also assume that sorting by section means sorting by term and then by
+section number. The result will therefore have a total of six columns.)
+*/
+
+/*
+The ratio of professors in pure math (PM) to professors in applied math
+(AM) who have taught a class in which the average grade obtained in the
+class was greater than 77.
+*/
+
+/*
+For the current term, report how many courses there are in the schedule
+with a particular number of classes. For example an output
+{[5, 1], [4, 2], [1, 5]}
+indicates that there are 5 courses with a single class (section), 4 courses
+with 2 classes, and 1 course with 5 classes scheduled in the curent term.
+*/