importer: change simple queries into parameterized queries

This commit changes simple queries (queries that are just single line or trivial to change) into paramterized queries. Moving forward, we should consider using parameterized queries for all queries we have.

The benefit is that we can get rid of current approach of using self.values_and_fields & self.q, which is sort of hacky. The drawback, however, could be some performance impact because we're going to rely on python package to handle formatting for us.