Using Arel/ActiveRecord to execute a subquery, including a SUM.

select_from_subquery.sql

select fund_sums.total, fund_products.name
from (
  select sum(allocation_amount) total, fund_product_id
    from transactions 
    where transactions.investor_id = 490
    group by fund_product_id
) fund_sums
left join fund_products on fund_sums.fund_product_id = fund_products.id

@stevenharman Thanks for this gist. It helped a lot. What is the magic of this:

manager = Arel::SelectManager.new(tt.engine)

Why .engine?