Writing SQL Using Request.form.item(i)

I am using the following to create an SQL statement
using the names and values from request.form.
The loop goes through each item in request.form

The issue comes in having an additional "and" at the end
of the loop and the value of x3 as not all options may be selected
from the form yet the loop goes through the entire request.form list

I have to add addtional code to strip off the last "and"
and was wondering if there is a way to eliminate the additional
code needed for stripping the "and".

Is there a way to determine which is the very last request.form.item(i)
that has a .key value and use that as x3? I would imagine I would not
need the additional code if there is a way to determine this. Code: