how to sum a column per variable that changes

[PaigeMiller]

Okay what happened here? There was a response from you that showed a table in which 0202 was changed to 0101, and now it is gone. Did you do that or did the SAS Communities do that?

[neo_noone]

Nope wasn't me. let me just update it

original

date	first_id	second_id	expenses
jul2020	400	0101	1000
jul2020	500	89	2001
aug2020	400	0202	1500
aug2020	500	89	2001
sep2020	402	0101	3200
sep2020	500	89	2001
oct2020	403	101	200
oct2020	500	89	2001
nov2020	400	202	100
nov2020	500	89	2001

the target table

date	first_id	second_id	expenses
jul2020	400	0101	1000
jul2020	500	89	2001
aug2020	400	0101	1500
aug2020	500	89	2001
sep2020	400	0101	3200
sep2020	400	89	2001
oct2020	400	0101	200
oct2020	500	89	2001
nov2020	400	0101	100
nov2020	500	89	2001

[PaigeMiller]

how about this:

data have; 
input date :monyy7.	first_id $	second_id $	expenses;
format date monyy7.;
cards;
jul2020	400	0101 1000
jul2020	500	89 2001
aug2020	400	0202 1500
aug2020	500	89 2001
sep2020	402	0101 3200
sep2020	500	89 2001
oct2020	403	0101 200
oct2020	500	89 2001
nov2020	400	0202 100
nov2020	500	89 2001
;
proc sort data=have;
    by first_id date;
run;
data want;
    set have;
    by first_id;
    retain second_id1;
    if first.first_id then second_id1=second_id;
    drop second_id;
run;
proc sort data=want;
    by date first_id;
run;

although I'm still not sure about your question about sums, what sums do you want from this table? Please show me. (Also, why does second_id even matter?)