You could do several things short of an array.  For example:

for x in $( db2 -x "select...")
 do
    yada yada yada
 done

or

db2 -x "select  x, y, z from ..." | read x y z
 do
     yada yada yada
 done

But the problem with ksh arrays I've worked with is knowing how many
elements you'll have so I guess you could do something like this. (
forgive me because I syntax may be off because I'm using windows right
now and don't have access to ksh )

counter=1
for x in $(db2 -x "select y from...")
 do
    arr[${counter}]=$x
    counter=$(($counter+1))
 done

The problem with this approach would be only being able to select one
column with the query.

HTH