Try this:
select distinct a.*, b.name as itemname,
(select top 1 c1.barcode from itembarcode c1 where c1.item_id=c.item_id)
from
table1 a,item b,itembarcode c where
b.id=a.item_id and c.item_id=a.item_id
Suggest you learn to use
JOIN [
^] in future.