In that example I don't care about the parents without children, but I guess the lighter way to do that is to add the having clause like:
Selectcount(tablechild.someid) as itemcount, tableparent.description ;
from tableparent ;
left outer join tablechild ;
on tablechild.someid = tableparent.someid ;
groupby tableparent.someid,tableparent.description
having itemcount>0