大概是这个意思：

proc sql;
create table newtable as
select a.*, b.var1, b.var2, ...
from old_table1 a left join old_table2 b
on a.id=b.id;
quit;

merge也可以，需要放左边的数据集写在左边

多谢,多谢,多谢

proc sort data=a1;by id;run;
proc sort data=a2;by id;run;
data a3;
merge a1(in=a)
           a2
;
by id;
if a;
run;

{:3_42:}