data allvar;
set sashelp.vcolumn;
where libname="WORK" and memname="A";
keep name;
run;

data _null_;
set allvar;
call execute('proc sql;
               create table varnobs'||cats(_n_)||' as
               select '||quote(strip(name))||' as varname, count(distinct '||strip(name)||') as nobs
               from a;
               quit;');
run;

data nobs;
set varnobs:;
run;

proc sql noprint;
select varname into: dropvar separated by " "
from nobs
where nobs=1;
quit;

data wanted;
set a;
drop &dropvar;
run;

input之后被吞了两个dollar符号

感谢大神！！！