1 vatarebt amas
---------------------------------------

 update t1 
 set t1.gacera=gac.raod
  from  itn_soft.dbo.GETPRODUCT as t1
  
 left join ( SELECT barcode, faqtura , SUM(CAST(raodenoba as decimal (18,4))) as raod  
FROM [ITN_SOFT].[dbo].gacera GROUP BY barcode,faqtura )as gac
on gac.barcode = t1.shtrixkodi 
and gac.faqtura=t1.zednomeri









2 vatarebt amas

---------------------------------------

 update t1 
 set t1.gacera='0'
  from  itn_soft.dbo.GETPRODUCT as t1
  
where t1.gacera is null