I have a Select command similar to the following

      SELECT key, valuea, sun(valueb) from table 
            order by key
            where between(date,startdate,enddate)
            into array a 

My problem is that I can get 1 to 3 rows in the array depending on the data. What I want is to always get 3 rows with zero for non-existant values. For example assume only key2 has a data. I then want the result like

        key1    0
        key2   12
        key3    0

What is the best way of doing this?