Why does select max(..) sort?

Hello

I am wondering why Oracle sorts a table in order to do a select max (..):

explain plan for select max(n) from test_for_max;

->

SELECT STATEMENT ()
 SORT (AGGREGATE)
  TABLE ACCESS (FULL) TEST_FOR_MAX It seems to me that the sort is unnecessary because while a table scan is performed on test_for_max, Oracle could compare an internal variable max_so_far with the current value of n and set max_so_far equal n if n is larger.

pseudo code

max_so_far = -INFINITE;
while (row* r=get_a_row_from_table(test_for_max)) {   if (r->n > max_so_far) max_so_far=n;
}
return max_so_far;

TIA Rene

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