Extract an update's "set field = value, field2 = value2" clause from the query. Uses a two-pass
match, unlike the other parsers here: the set clause's own boundary is found first (so it can
be removed from the query as a whole, and so the comma-separated list doesn't get confused with
anything that follows, like a where clause), then each individual assignment is parsed out of
that captured substring.
Extract an update's "set field = value, field2 = value2" clause from the query. Uses a two-pass match, unlike the other parsers here: the set clause's own boundary is found first (so it can be removed from the query as a whole, and so the comma-separated list doesn't get confused with anything that follows, like a where clause), then each individual assignment is parsed out of that captured substring.