Output not sorted when using group by clause

Question

Recently we migrated our application from Forms5 to Forms10g and database from 7.3.2 to 10gR2.
More than 400 applications using sql stmt with "group by" clause and without "order by".
In Earlier version of oracle 7.3.2 "group by" clause in SQL stmt sorts the output by order of the column in the "group by"
stmt, where new version of oracle 10g (10.2.0.1.0 - 64bit Production) doesnt behave like older version.
eg select div_cd,dept_cd,count(*) from class group by div_cd,dept_cd
Output of the above query in Oracle7
DIV_CD DEPT_CD COUNT(*)
0 1     120
0 9 131
1 4 938
1 6 1
4 1 1490
5 2 59
6 6 848
6 9 295
8 1 45
9 5 19
Output of same query in Oracle10g
DIV_CD DEPT_CD COUNT(*)
0 6 120
0 9 131
4 1 1490
6 9 295
8 1 45
9 5 19
1 4 938
1 6 1
5 2 59
6 6 848
My question is
a) Does the oracle behave in that manner?.
b) if so, Any patch set available for this?
c) if no patch set how to resolve this issue.
if i use "order by" clause
along with group by then i can get the output how i want.
BUt problem is more than 400 applications (forms) using above method.
Identify Forms/Reports and rectifing is a tedious job.
Anyone can give me a good solution to solve the above issue

Answer 1

Group By does not, and never has guaranteed order. Just because it happened that way on the past does not mean it will continue to do so.
In the past, the algorithm used for Group By invoked a sort. It was convenient for the system to simply dump the output in that resulting order. These days, Group By could also be accomplished using a hash algorithm. Walking through the hash can easily result in a completely different ordering, as you have seen.
Your problem is that the assumptions made previously are now invalid. Oracle is still working correctly. No patch, but you might be able to work around it by crippling your database and using the COMPATIBLE parameter (although the official lower limit is 9.2.0)