DM 'CLEAR LOG';
DM 'CLEAR OUTPUT';
OPTIONS LINESIZE=72 NODATE NONUMBER;
DATA   file1;
       INFILE 'a:\concat1.txt';
       INPUT w x y $ z;
PROC SORT DATA=file1;
          BY y;
DATA   file2;
       INFILE 'a:\concat2.txt';
       INPUT w x y $ z;
PROC SORT DATA=file2;
          BY y;
DATA   file3;
       SET file1 file2;
       BY y;
PROC PRINT DATA=file3;
     TITLE 'Result of SET with a BY statement';
DATA   file4;
       SET file1 file2;
PROC PRINT DATA=file4;
     TITLE 'Result of SET without a BY statement';
RUN;