Is it possible to create a Select Query in Access so that it affects (or
changes) the data table or tables it uses for its results?
No, but a Select query can be editable in its own right, so that a user can
open it as a datasheet and change data; or (more appropriately) used as the
Recordsource for a Form which again can be used to edit data. The data will
indeed be changed in the underlying tables; the query has no independent
existance.
Not all Select Queries are updateable but most are, or can be made so.
