Unable to aggregate or join query (Side by side) into single one (1 Viewer)

Hello, MS Access expert.
I am so novice Access user. I have created a Access Database to calculate GPA for student.
There are eight table containing one to one relationship for eight subject and query for each table.
When i try to join eight query (side by side) into single one, it shows me "query is too complex" though the all query works fine individually.
Can anyone help me how to join all query into single query or how to fix "query is too complex".
N.B: There are many immediate IIF in a query, any idea of its equivalent?

your design is wrong. It is not relational.
It should be only 2 tables, like:

tStudentWork table
----------------
StudentID -long
AssignID -long
Grade -single
Note -str



tClassAssigns table
----------------
AssignID -auto
ClassID -long
AssignName -str.
AssignType -(quiz,homework, assignmt, lab)
AssignDate -date
DueDate -date
TotalPts -single

The way you have it now you will need to make 1 query for each table for each field.
then put all the queries into a UNION query ,
then sum the union query.