SQL Server 2008 med COUNT() OVER
select *, c = count(1) over (partition by zip)
from tbl
order by c desc;
Om du inte behöver se den extra kolumnen kan du flytta COUNT() OVER
in i ORDER BY-satsen.
select JobCode, Job1, Job2, Job3, zip
from tbl
order by count(1) over (partition by zip) desc;