MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table mytable (
  CALMONTH int,   
  COSTCENTER varchar(20),
  Kontonummer int,
  FIELDNM003 int
);

insert into mytable values
(202212,      'Alpha',      123,          10),
(202301,      'Alpha',      123,          20),
(202210,      'Alpha',      223,          50),
(202307,      'Beta' ,      123,          10);

Records: 4  Duplicates: 0  Warnings: 0


select COSTCENTER, Kontonummer
from mytable
where CALMONTH >= 202301
group by COSTCENTER, Kontonummer


COSTCENTER
Kontonummer


Alpha
123

Beta
123


SELECT t.*
FROM mytable t
inner join (
  select COSTCENTER, Kontonummer
  from mytable
  where CALMONTH >= 202301
  group by COSTCENTER, Kontonummer
) as s on s.COSTCENTER = t.COSTCENTER
       and s.Kontonummer = t.Kontonummer


CALMONTH
COSTCENTER
Kontonummer
FIELDNM003


202212
Alpha
123
10

202301
Alpha
123
20

202307
Beta
123
10