Data Left_outer;
set data1(in=x) data2(in=y);
if x=0 and y=1;
run;

dnt use set it wnt work.
use merge with in statements as above.

There is no such Inner & Left Joins.  In SAS only one join 
i.e Right Join.  If you want Left Join you have to use the 
data set in the second place. For example: D1 D2 are the 
data sets for D2 you want to make, UPDATE D1 D2;

Data left_outer;
merge emp(in=a) dept(in=b);
by deptno;
if a=1 and b=0;
run;