Sorry, I initially misunderstood the problem.
Here's my modified post.
Create a view over the each dataset and convert the variable (alpha) to an numeric equivalent.
[pre]
proc sql noprint;
create view X1 as
select var1, input(var2,best.) as VAR2 from INDATA1;
quit;
proc sql noprint;
create view X2 as
select varX, input(var2,best.) as VAR2 from INDATA2;
quit;
[/pre]
then merge the views into a single dataset.
Should work.
Cheers from Portugal
Daniel Santos @
www.cgd.pt