Хотели бы вы этого?
---drop table test
create table test
(ITEMID varchar(20),
Qty decimal(10,2),
TMonth int,
TYear int)
insert into test values
('01.0002',392.00,1,2019),
('01.0002',392.00,2,2019),
('01.0002',392.00,3,2019),
('01.0002',784.00,4,2019),
('01.0002',784.00,5,2019),
('01.0002',392.00,6,2019),
('01.0002',784.00,7,2019),
('01.0002',392.00,8,2019),
('01.0002',392.00,9,2019),
('A0-B1002',300.00,8,2019),
('A0-B1002',3000.00,9,2019),
('ZX-YT12',5.00,1,2019),
('ZX-YT12',5.00,2,2019),
('ZX-YT12',5.00,3,2019),
('ZX-YT12',5.00,4,2019),
('ZX-YT12',5.00,5,2019),
('ZX-YT12',5.00,6,2019),
('ZX-YT12',20.00,7,2019)
select ITEMID,sum(Qty) as Qty, count(TMonth) as MnthCount
from test group by ITEMID
/*
ITEMID Qty MnthCount
-------------------- --------------------------------------- -----------
01.0002 4704.00 9
A0-B1002 3300.00 2
ZX-YT12 50.00 7
*/