谢谢您的回答，确实是label。现在的麻烦是由sas输出的s1，s2.。。。。等table中第二列的name都是num，这样怎么才能合并呢？改name？谢谢您的回答。
btw：我怎么才能再赠送您论坛币呢

data s1;
input date $9. num@;
datalines;
2010-3-1         334
2010-3-2         786
2010-3-3         378
;
run;
data s2;
input date $9. num@;
datalines;
2010-3-1         124
2010-3-2         346
2010-3-3         675
;
run;
/*        ********用sort+merge************************************************************************
proc sort data=s1 out=s1(rename=(num=num1));
by date;
run;
proc sort data=s2 out=s2(rename=(num=num2));
by date;
run;
data result;
merge s1 s2;
by date;
drop date;
run;
*/
/*        *******SQL***********************************************************************************
proc sql;
create table resultsql as select s1.num as num1,s2.num as num2 from s1 join s2 on s1.date=s2.date;
quit;
*/
/*        APPEND+LAG*************************************************************************************
proc append base=s1 data=s2;
run;
data s1;
set s1;
num1=lag3(num);
if num1^=.;
drop date;
run;
*/

还有一个方法就是
data s1;
input date $9. num@;
datalines;
2010-3-1         334
2010-3-2         786
2010-3-3         378
;
run;
data s2;
input date $9. num@;
datalines;
2010-3-1         124
2010-3-2         346
2010-3-3         675
;
run;
data _null_;
set s2;
call symput("num"||left(_n_),num);
run;
data s1;
set s1;
num2=symget("num"||left(_n_));
drop date;
run;

非常感谢版主啊，解决了