delete null columns

%macro delete_empty;
ods select none;
ods output nlevels=temp;
proc freq data=sv10 nlevels;
 tables _all_;
run;
proc sql;
 select tablevar into : drop separated by ','
  from temp
   where NNonMissLevels=0;

  alter table sv10
   drop &drop;
quit;

%mend delete_empty;
%delete_empty