/* These are the same data sets we saw before with a couple  */
/* records added to both                                     */
data a;
input x y z;
datalines;
1 3 7
2 4 8
1 4 10
3 3 .
2 1 6
2 2 .
;
run;
data b;
input x y zz;
datalines;
1 3 9
3 4 6
3 3 .
2 4 .
2 2 7
1 1 9
;
run;
proc sort data=a; by x y;
proc sort data=b; by x y;
run;

/* Note that from_a and from_b aren't saved     */
data dd; merge a (in=from_a) b (in=from_b); by x y;
if from_a=1;
proc print data=a;
proc print data=b;
/* The unmatched x,y pairs in b--(1,1) and (3,4) are not included in dd */
proc print data=dd;
title 'Data with x,y pair in a';
run;
/* Save the data set indicators             */
data dd; merge a (in=from_a) b (in=from_b); by x y;
save_a=from_a;
save_b=from_b;
proc print;
run;