I'm not sure whether you can or not in 9.0 (I don't have it), but if not, it might be because 9.0 adds the new feature "Add Command." This would be one of your datasource options when you first start designing your report. It allows you to write a SQL statement from scratch. You could probably copy the show SQL query from an existing report into the Add Command area for a new report and then modify it as necessary.
-LB