I need to create AJOINID variable as given in XLSx file

[Tom]

Again I am not sure why it matters what numbers are used.  I would also push back on that requirement to see if there is any basis for it.

You can always renumber.

proc sort data=test;
  by usubjid aellt astdt fake_end ;
run;

data step1 ;
  set test ;
  by usubjid aellt ;
  if first.usubjid then GROUP=0;
  if first.aellt or (astdt > lag(aendt)) then GROUP+1;
run;

proc sql ;
create table renumber as  
  select usubjid,GROUP,aellt,min(astdt) as first_date format=date9.
  from step1
  group by usubjid,GROUP,aellt
  order by usubjid,first_date,aellt
;
quit;

data renumber;
  set renumber;
  by usubjid first_date aellt;
  if first.usubjid then AJOINID=0;
  AJOINID+1;
  keep usubjid GROUP AJOINID;
run;

proc sort data=renumber;
  by usubjid group;
run;

data want;
  merge step1 renumber;
  by usubjid group;
run;

proc sort data=want;
  by usubjid astdt aellt fake_end ;
run;

proc print;
run;