select l.loan_id as loan,
       p0.amount as amount,                                                                                           
       sum(p1.amount) as amountPayed
from loans l                       
        inner join account_histories p0
        on l.loan_id = p0.loan         
           left outer join account_histories p1
           on l.loan_id = p1.loan and p1.from_account = 1945
where p0.to_account   = 1945 and p0.from_account = 1
group by l.loan_id

select
    l.id,
    p.amount,
    sum(p1.amount)
from
    Loan l inner join l.loanPayments p left join l.loanPayments p1
where (p.from.id=1 and p.to.id = 1945) and p1.from.id = 1945
group by l