SQL & PL/SQL :: How To Write Correlated Sub Query

I have employee, location, city tables, I have written following code to use joins

select ename from employee e, location l, city c
where e.c_locationid= l.locationid and l.cityid= c.cityid and c.cityname='XYZ';

The same can be written by using non- correlated sub query as follow..

select ename
from employee
where c_locationid in (select locationid from location where
cityid in (select cityid from city where cityname='XYZ'))

I need to implement the same concept using correlated sub query...