create table A (htbh varchar(10), htlx int, htje decimal)
insert into A values ('0001', 1, 5000.00)
insert into A values ('0002', 1, 8000.00)
create table B (htbh varchar(10), skbh varchar(10), ysje decimal, payed decimal)
insert into B values('0001', '01', 2000.00, 2000.00)
insert into B values('0001', '02', 1500.00, 1000.00)
insert into B values('0001', '03', 1500.00,null)
insert into B values('0002', '04', 1500.00,100)
select A.htbh, A.htlx, A.htje, sum(B.payed) as sum
from A, B
where A.htbh = B.htbh
group by A.htbh, A.htlx, A.htje
--or
select htbh, htlx, htje, (select sum(payed) from B where B.htbh = A.htbh) as sum
from A