SQL Server 2008 utilizzando COUNT() OVER
select *, c = count(1) over (partition by zip)
from tbl
order by c desc;
Se non hai bisogno di vedere la colonna aggiuntiva, puoi spostare COUNT() OVER
clausola nella clausola ORDER BY.
select JobCode, Job1, Job2, Job3, zip
from tbl
order by count(1) over (partition by zip) desc;