the worksheet sql is always structured according to the EUL (end user layer) . if you have used two clients tables and created a join to different tables then the sql will be generated as per your requirement . there is no way we can have Discoverer create a sql like that . if you are so interested with the sql . you can create a custom folder in the business area and paste the sql and create a report on top of the custom folder .
you can always edit the heading in the discoverer plus workbooks as per your requriement
hope this helps