data a;
input x y$@@;
cards;
1 r
;
run;
data b;
input x z$@@;
cards;
2  g
;
run;
data c_1;
set a b;
run;
proc  sql;
create table c as
select  a.x,a.y
from a
union all
select b.x,b.z
from  b
quit;

怎么样用proc sql  做成的dataset 和用set 做的c_1 是一样的