Some aggregates can not be used over subqueries.
select a.name, sum(a.amount) from (select name as name, amount as amount from EntityB) as a group by a.name
is not working in both 6.1 and 6.2 versions
select a.name, min(a.amount) from (select name as name, amount as amount from EntityB) as a group by a.name
and
select a.name, max(a.amount) from (select name as name, amount as amount from EntityB) as a group by a.
are not working in 6.1, but working in 6.2