SQL/MySQL/ORACLE DBA Learning

select (select m3.bal     from tlm_gt_custom m3    where m3.acc = m1.acc      and m3.ccy = m1.ccy      and trunc(m3.val_dt) >= trunc(add_months(sysdate, -1), 'MM')      and rownum = 1) begining_of_month        from tlm_gt_custom m1 where m1.ccy = 'USD' and m1.acc = '9820084080783001'   group by m1.ccy, m1.acc How to display 0 if there is no data in the above query