data a;
input x y $ @@;
cards;
1 a 2 b 3 c 4 d
;
data b;
input z @@;
cards;
1 2 3
;

* --- Merge;
data wanted;
merge a b(rename=(z=x) in=b);
by x;
if b;
run;

* --- Sql;
proc sql;
create table wanted as
select * from a
where x in (select distinct z from b);
quit;

已经做出来了，非常感谢！