Generate a report based on a group of check-boxes

I'm trying to generate a report based on a group of check-boxes that represent all db tables and a group of dependent check-boxes that represent all columns in each table.

So I created a form that contains 8 check-boxes (tables) if the user checked one all its columns will be listed as a new check-boxes below it, So he can check the columns to include in the report. Subsequently, my form has 48 check-boxes.

My Question

What is the most efficient way to receive only what he checked and execute a general join query that will work no matter what he choose ?

I'm having a hard time in writing that smart query :")