/*
Find sname of suppliers who ships to every city
        where there is a project taking place.

select distinct sname
from supplier S
where
       { city of proj supplied to by S }
       contains
       { city where a proj takes place}
where NOT EXISTS
       { city where a proj takes place}
      - { city of proj supplied to by S }
*/

select distinct sname
from supplier S
where not exists (select *
                  from proj
                  where 
			city in (select city  /* City that proj takes place */
                                 from proj)
                    and 
			city not in (select city /* city of proj suppl by S */
                                     from   proj, spj 
                                     where spj.jnum = proj.jnum
                                     and   spj.snum = S.snum)
                 )
order by sname

