Try something like this...
select Sector,
(select count(type) from sectors b where a.sector = b.sector and type = 'X') AS "Nr of X",
(select count(type) from sectors b where a.sector = b.sector and type = 'Y') AS "Nr of Y",
(select count(type) from sectors b where a.sector = b.sector and type = 'Z') AS "Nr of X"
from Sectors a
group by sector