select e.ename,e.sal,

coalesce(

(select min(sal) from emp d where d.sal>e.sal),

(select min(sal) from emp)

) as forware,

coalesce(

(select max(sal) from emp d where d.sal<e.sal),

(select max(sal) from emp)

) as rewind

from emp e

order by 2;