Hello,
We have an application which gives the users the option to build on-
line queries which will retrieve data from the Oracle 9i database in
ANY way they want.

The obvious problem we have is that some queries executes full table
scans in very big tables, all sorts of bad queries have been issued by
the users - and the system performance is currently very bad!

My question is: is there a way to prevent the users to run very bad
queries? I mean, if the application can check that the query doesn't
have "enough arguments" or has a very high cost and return a warning
message to the user, telling him that this can not be executed.

Another idea would be configure something inside oracle to prevent
"very bad" queries to be executed ...

Does anyone have any ideas about it?

Many thanks in advance!
Ana