Changing tables for module storage using administration form fields

I'm looking to create some basic text fields which will introduce logic inside of database queries which is done.
Unfortunately there's a compatibility problem where the database doesn't exist when submitting the form.

Can anybody provide examples of a hook_form_submit() where:
- vget is used to install a module's schema in a table of the same value as the variable, or
- the same function as the first point but instead of simply changing the reference, migrating all data into a new table with the existing schema and removing the old.

I can't find any working examples using this functionality, the submit button simply breaks into a PDO Exemption.
I could supply some code examples, but none have worked so far in the same extent as being usable.