This is to show: in proc sql group by statement, select should only contain group by vars and summary vars(vars to be summarized). Otherwise the result may be totally different from wanted.
data a;
input id a $2. value;
cards;
1 a 12
2 b 112
3 c 1121
1 a 3
2 b 23
3 c 15
1 a 16
;
run;
/* include both id and a in the select statement */
proc sql;
select id, a, sum(value) as v
from a
group by id;
quit;
/* include only id in the select statement */
proc sql;
select id, sum(value) as v
from a
group by id;
quit;
endsas;
/* output for include both id and a: there are duplicates */
id a v
----------------------
1 a 31
1 a 31
1 a 31
2 b 135
2 b 135
3 c 1136
3 c 1136
/* outpur for include only id */
id v
------------------
1 31
2 135
3 1136
