If is null then 0

Question

Code working fine, just need to replace last line 6 to be:

 

IF IS null then 0

 

Some help

 

select x1.naziv, x1.Nabavka, x2.Prodaja, x1.Nabavka-x2.Prodaja as 'Stanje' from (select naziv, sum(kolicina) as Nabavka from
( select naziv as naziv, convert(float, kolicina) as kolicina from ulazni_racun_roba_roba union all select naziv as naziv, convert(float, kolicina) as kolicina from mp_ulazni_racun_ostalo_roba ) a
group by naziv) x1 left join ( select roba, sum(kolicina) as Prodaja from
( select roba, convert(float, kolicina) as kolicina from mp_racun_roba union all select roba, convert(float, kolicina) as kolicina from mp_faktura_roba ) b
group by roba ) x2 on x1.naziv = x2.roba
where x2.roba is not null