2         data data1;
3           subject = 1001; output;
4           subject = 1002; output;
5           subject = 1003; output;
6         run;

NOTE: Data set "WORK.data1" has 3 observation(s) and 1 variable(s)
NOTE: The data step took :
      real time : 00:00:00.030
      cpu time  : 00:00:00.000


8         data data2;
9           subject = 1001; output;
10          subject = 1002; output;
11          subject = 1004; output;
12        run;

NOTE: Data set "WORK.data2" has 3 observation(s) and 1 variable(s)
NOTE: The data step took :
      real time : 00:00:00.010
      cpu time  : 00:00:00.010


14        data data3;
15          subject = 1001; output;
16          subject = 1004; output;
17          subject = 1005; output;
18        run;

NOTE: Data set "WORK.data3" has 3 observation(s) and 1 variable(s)
NOTE: The data step took :
      real time : 00:00:00.010
      cpu time  : 00:00:00.000


20        data out;
21          merge data1 (in=a) data2 (in=b) data3 (in=c);
22          by subject;
23          source = 100*a + 10*b + c;
24          put subject= source= z3.;
25        run;

subject=1001 source=111
subject=1002 source=110
subject=1003 source=100
subject=1004 source=011
subject=1005 source=001
NOTE: 3 observations were read from "WORK.data1"
NOTE: 3 observations were read from "WORK.data2"
NOTE: 3 observations were read from "WORK.data3"
NOTE: Data set "WORK.out" has 5 observation(s) and 2 variable(s)
NOTE: The data step took :
      real time : 00:00:00.020
      cpu time  : 00:00:00.000