How To Compare Values From Same Table

I need comparing value from the same table for my final project.
Example :
Table 1 :
SubjectCodeClasses
Sub Aclass 1
Sub Aclass 2
Sub Aclass 3
Sub Bclass 2
Sub Bclass 3
Sub Bclass 4
Sub Bclass 5
Sub Cclass 6
Sub Cclass 7
Sub Cclass 8
...

My task is, I need to compare the classes in the subject. Sub A with class 1, class 2, class 3 have to compare with Sub B and Sub C. if classes from Sub A exist in Sub B then the output is 0, if not the output is 1. then Sub A again will compare with Sub C and the rest. After Sub A compare its value with other subject. Sub B will start comparing with all the subject and so on.

Below is the concept.
Sub ASub BSub C
Sub A001
Sub B000
Sub C100
I really don't know to do the loop..