ORA-00935: group function is nested too deeply - SQL Query is correct...

Question

select s.sname, to_char(sum(t.amount), 'fm$999999.00')
from transactions t, salespeople s
where t.sid = s.sid
group by s.sname, t.year
having (t.year = 1997) and max(sum(t.amount));
I'm trying to print sales person name who had the highest total sell in 1997. I do not see where did i go wrong in the above query...Isn't nested group function allowed?!
What about this?
select s.sname, to_char(sum(t.amount), 'fm$999999.00') as "TOTAL"
from transactions t, salespeople s
where t.sid = s.sid
group by s.sname, t.year
having (t.year = 1997) and sum(t.amount) = (select max(amount) from transactions where year = 1997);
It should return something, but it does not due lack of data in database. I think the above code is correct. I just need to confirm from you...

Answer 1

select s.sname, (case when sum(t.amount) > sum(t2.amount)
then sum(t.amount)
else sum(t2.amount)
end) "TOTAL"
from transactions t, salespeople s
where t.sid = s.sid
group by s.sname, t.year
having t.year = 1997
union
select s.sname, sum(t2.amount)
from transactions t2, salespeople s
where t2.sid = s.sid
group by s.sname, t2.year
having t2.year = 1997;
Your code looks good, but it does not work in Oracle Developer...
The above should work isn't it? The inner query gets executed then the outer one so the result i get in