Can any Java expert help me? Urgent.

Question

I create a table---CourseDB in adatabase to store the Student ID ( student identification number) and the grades of the courses that they took.
The structure of the table---CourseDB is:
StudentID
GradeofCourse1
GradeofCourse2
GradeofCourse3
GradeofCourseN
Here GradeofCourse1 means the grade of course 1, that the student obtained. GradeofCourse2, GradeofCourse3, GradeofCourseN have the same meaning.
I want to use the following query to count the students
who get g1 in course 1, and g2 in course 2, ......and gn in
course n.
Select COUNT(*)
From CourseDB
Where GradeofCourse1=g1 AND GradeofCourse2= g2
......AND GradeofCourseN=gn
Here g1, g2,......,gn are grade, the values are: A,B,C,D.
I want to consider all the possible combination of g1,g2,...,gn.
The students take all the n courses:Course 1, Course 2,...., Course n, and may get A,B,C, or D in the n courses.
For example:
g1=A,g2=B,g3=C,.....,gn=D
( This means that the student gets A in Course 1, gets B in Course 2, gets C in Course 3,....., gets D in Course n. Many students may have the same situation. I want to know how many are the students?)
Or:
g1=B,g2=C,g3=D,......,gn=A
To make the problem clear, I give a detail example:
For example, there are two courses: course 1, course 2.
I want to know how many stuent get "A" in course 1 and
get "B" in course 2 at the same time.
And I want to know all the grade combination of the two courses:
course 1 course 2
A A
A B
A C
A D
B A
B B
B C
B D
C A
C B
C C
C D
D A
D B
D C
D D
So that's 16 total combinations(4^2).
My question is in the code how I can assign the values(A,B,C,D)
to g1,g2,g3,.....,gn conveniently.
The following "nested for loop" can solve the problem ( for example, there are 6 courses):
for (char class1 = 'A'; class1 <= 'D'; class1++)
for (char class2 = 'A'; class1 <= 'D'; class2++)
for (char class3 = 'A'; class1 <= 'D'; class3++)
for (char class4 = 'A'; class1 <= 'D'; class4++)
for (char class5 = 'A'; class1 <= 'D'; class5++)
for (char class6 = 'A'; class1 <= 'D'; class6++)
select count(*)
from CourseDB
where GradeofCourse1=class1 AND GradeofCourse2 = class2 AND GradeofCourse3 = class3
....AND GradeofCourse6=class6
But the problem is that in the "Where GradeofCourse1=class1 AND
GradeofCourse2= class2 ......AND GradeofCourse6=class6" of the
Query, the number of courses is not fixed, maybe six, maybe three,
maybe four, so the depth of "nested for loop" can not be fixed.
Can any Java expert give me some suggestions?
Thanks in advance.
Jack

Answer 1

Jack,
When you posted this on the other forum, it was quite a different question, but it has mutated to this point now. I believe what you want to do can be done with what MS Access calls a crosstab query and you can completely leave Java and any other programming language out of it. If you need to know how to do a crosstab query please take it to another forum.