How do I create a sort variable that restarts the count when a new subject occurs in the next rows?

[Hello_there]

Hello,

I'm trying to create a sort variable that restarts every new subject.

data have;
	input subject $;
datalines;
001
001
002
003
003
003
004
006
007
007
008
;
run;

desired output:

[PaigeMiller · Accepted solution]

data want;
    set have;
    by subject;
    if first.subject then sort=0;
    sort+1;
run;

[Hello_there]

Thanks, PaigeMiller, this worked!

[Kurt_Bremser]

data want;
set have;
by subject;
if first.subject
then sort = 1;
else sort + 1;
run;

Use of a SUM statement causes an implied retain.