OPTIONS LS=64 PS=66 NONUMBER NODATE;

****************************************;
*** Merging datasets by observations ***;
***  which are properly ordered and  ***;
***     have no common variables     ***;
****************************************;

DATA m1;  INPUT x1 x2 @@;
          n=_n_;
CARDS;
 2 3   4 4   6 8    8 9    9 7

DATA m2;  INPUT y1 y2 @@;
          n=_n_;
CARDS;
 15 123  11 131  12 155  19 211  22 256

DATA both; MERGE m1 m2; BY n;

PROC PRINT DATA=both;  ID n;
RUN;