Tips for derived tables in SQL and using FULL OUTER JOINs

I'm not sure why it isn't working for you, unless perhaps you're using MySQL, which doesn't support FULL OUTER JOIN. But in that case you should've received an error message, rather than no results.

Here's an alternate strategy:

SELECT usr
     , SUM(CASE WHEN act = 'ADD'
                THEN 1
                ELSE 0 END) AS ADD
     , SUM(CASE WHEN act = 'UPD'
                THEN 1
                ELSE 0 END) AS UPD
  FROM RGS8 
 WHERE act IN ('ADD','UPD') 
   AND dte = 20080310 
GROUP 
    BY usr

This should perform better as well, since it requires only one pass of the table.