data want;
set have;
       Old_Occupation=Occupation ;
       countnumber=countw(Old_Occupation);
           if countnumber=0 then
       output;
         else do i= 1 to (countw(Old_Occupation));
           Occupation = scan(Old_Occupation, i,' ');
         output;
         end;
      drop i Old_Occupation;
run;

忘了分隔符是“；”
data want;
set have;
       old_Occupation=Occupation ;
       countnumber=countw(old_Occupation);
           if countnumber=0 then
       output;
         else do i= 1 to (countw(old_Occupation));
           Occupation = scan(old_Occupation, i,';');
         output;
         end;
      drop i old_Occupation;
run;

谢谢大佬