SQL & PL/SQL

hi,
is there any difference between the below FOR loop and WHILE loop? both seems to do the same work.
Please correct me if i'm wrong

for i in persons.First .. persons.Last loop
yourAssocArray(persons(i).ID) := persons(i).Name;
end loop;
----------------------------------------------

i := persons.First
while i is not null loop
yourAssocArray(persons(i).ID) := persons(i).Name;

i= persons.next;
end loop;