data have; input Center $ FirstName001 $ FirstName002 $ FirstName003 $ LastName001 $ LastName002 $ LastName003 $; cards; A Jason Katie Peter Berkowitz. Basel Hirsch B Dawn Betty Chris Crane Barhaghi Choe C Andy Ben Donald Nassar Amidi Naomi D Andrew Ronald Chirsty Lee Hesham JoAnn E Lee Jennifer Louis Banooni Kimelman Douglas run; data want; set have; student001=catx("",FirstName001,LastName001); student002=catx("",FirstName002,LastName002); student003=catx("",FirstName003,LastName003); keep center student:; run; ... View more

data table1; input (_Name C1) ($); datalines; Thomas 2 Fabien 7 Nelson 9 ; data table2; input (_Name r1) ($); datalines; Thomas TB Fabien AB Didier Ajac ; run; proc sort data=table1;by _name;run; proc sort data=table2;by _name;run; data want; merge table1(in=a) table2(in=b); by _name; if a; if a and b then count=2; proc sort ;by _name; run; ... View more

In the given code you have 3 outputs right then it will give you 3 observations if you have 10 output statements then it will give you 10 observations.   firs toutput iteration: x,y have values and z is missing you given output statement so it will print values for x,y and z for missing. secondoutput iteration:z have value 50 so it will print z with 50 and you already ave x,y values so in second iteration it will print 10,20 as x,y values third output iteration: x,y,z contain values but you again assigned with 100 x value over write and y,z values as follows.   data new; x=10; y=20; output; z=50; output ; x=100 ; output ; run;     ... View more