data FirstTry; 
   input variablea variableb variablec;
datalines;
12   45   65
17   28   47
12   23   67
12   23   56
17   89   25
;
proc print data=FirstTry; run;

proc sort data=FirstTry; 
   by variablea variableb variablec; 
run;

proc print data=FirstTry; run;

proc univariate data=FirstTry; 
   var variableb;
run;