Conditional sum in SQL (SAS) (SUMIFS equivalent) - Part 2 - sql

Question

Let say I have to table:
Table1:
ID Item
1 A
1 B
1 A
2 B
2 B
3 A
3 B
3 B
3 A
Table2:
ID A B C
1 91 94 90
2 100 97 93
1 97 94 96
2 97 95 90
3 99 100 93
1 90 97 97
Now I would like to take the sum conditional for my table1 from table2 (when the ID by row and the Item match by COLUMN):
ID Item Want
1 A 278
1 B 285
2 A 197
2 B
2 B
3 A
3 B
3 B
3 A
So that I have 278 is the sum of all item 1 in column A, 285 is the sum of all itme 1 in column B, 197 is the sum of all item 2 in column A.
So what am I supposed to do in SQL?
Thanks in advance.

Answer 1

You can use join and conditional aggregation:
select t1.id, t1.item,
sum(case when t1.item = 'A' then t2.A
when t1.item = 'B' then t2.B
when t1.item = 'C' then t2.C
end) as want
from table1 t1 left join
table2 t2
on t1.id = t2.id
group by t1.id, t1.item

Answer 2

Proc MEANS is built from the ground up for the sole purpose of computing statistics for aggregates.
Consider this example:
data have; input
ID $ A B C; datalines;
1 91 94 90
2 100 97 93
1 97 94 96
2 97 95 90
3 99 100 93
1 90 97 97
;
ods _all_ close;
proc means data=have stackodsoutput sum;
class id;
var a b c;
ods output summary=want;
run;
that produces data set