Support UPDATE IF NOT EXIST OR compare checks in LWT transactions

I've got a column that I want to update e.g min = x IF min > x
but if there is no value for min e.g min == null then the update will never succeed, which means I need to do a READ then INSERT and then run UPDATES which defies the purpose of using the LWT for this use case.
is it possible for LWT to support either IF min > x OR min == null ? or otherwise take null as equal to zero for numbers ?