fixed stuff based on piazza posts

a2/a2.sql

@@ -7,15 +7,9 @@ name “computer science”.
 */
 select distinct sname, snum from student where year = 2 and snum in
 (
-  select snum from mark m1 where grade < 65 and deptcode in
+  select snum from mark m1 where grade < 65 and deptcode = "CS" and snum in
   (
-    select deptcode from department where deptname = "computer science"
-  ) /*having count(distinct section) > 1*/ and snum in
-  (
-    select snum from mark where grade < 65 and deptcode in
-    (
-      select deptcode from department where deptname = "computer science"
-    ) and snum != m1.snum
+    select snum from mark where grade < 65 and deptcode = "CS" and snum != m1.snum
   )
 )
 
@@ -49,22 +43,27 @@ select distinct snum, sname, year from student where snum in
 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 e.snum, e.deptcode, e.cnum, e.term, e.section from enrollment e where exists
   (
-    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 c.pnum, c.deptcode, c.cnum, c.term, c.section from class c where
+    c.deptcode = e.deptcode and c.cnum = e.cnum and c.term = e.term and c.section = e.section and c.pnum not in
     (
-      select pnum from professor where deptcode = prev_deptcode
+      select pnum from professor where deptcode != "CS"
     )
   )
 )
 
+select c.pnum, c.deptcode, c.cnum, c.term, c.section from class c where c.pnum not in
+(
+  select pnum from professor where deptcode != "CS"
+)
+
 /*
  A sorted list of all departments who do not have a professor currently
 teaching a course offered by a different department.