I have a query that gets some criteria (City and State) from a form.
I have the State field set up as a ComboBox connected to a local table
I created. If a user was to type in a City (i.e. "Springfield") and
then leave the State field empty, then the query would have no
results.

How do I make the query so that if one of the fields on the form is
left empty it will run for all possibilities (i.e. look for all
Springfields in any state)?