/* pgm 10.2                  */
 /*                           */
 /*  set with 'by' aka 'interleaving'    */
 /*                                      */
  data a ;                    * first dataset with w x y ;
    input w x y ;             * two observations ;
    cards ;
     2  1  4
     3  3  0
    ;
 run ;
  data b ;                    * second dataset with x y z ;
    input x y z ;             *  three observations ;
    cards ;
     2  1  0
     4  0  3
     6  2  2
    ; 
 run ;
 /* put them together         */
 /*   expect 5 obs and 4 vars */
   data aandb ;
     set a b ;
     by x ;                   * both a and b already in order by x ;
 run ;
 /* print them out            */
   proc print data=aandb ;
     title2 'by x' ;
 run ;