proc sql;
create table c as
select b.portfolio,a.code
from a,b
where a.begin<=b.portfolio<=a.end;
quit;

楼上，赞！我和楼上一样
data a;
input code begin :$7. end :$7.;
datalines;
1       2010/03      2011/02
2       2004/09      2005/08
3       2004/02      2005/01
;
run;
data b;
input portfolio :$7.;
datalines;
2005/01
2005/02
2005/03
;
proc sql;
create table chk as
select *
from a , b
where begin<=portfolio<=end
;
quit;
proc sort data=chk1;
by portfolio code;
run;
data chk2;
set chk1;
by portfolio code;
if first.portfolio then nord=0;
nord+1;
run;
proc transpose data=chk1 out=wanted(drop=_name_) prefix=out;
by portfolio;
var code;
run;

啊明白意思了，谢谢您！

谢谢！先匹配再transpose，明白了！