MariaDB 10.4

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create table temp_months (yr int, mth int, primary key (yr, mth));
insert into temp_months values
(2020, 1), (2020, 2), (2020, 3), (2020, 4), (2020, 5), (2020, 6),
(2019, 7), (2019, 8), (2019, 9), (2019, 10), (2019, 11), (2019, 12);

create table my_table (created_date date, company_id int, id int);
insert into my_table values
('2020-05-01', 123456, 1),
('2020-02-01', 123456, 1),('2020-02-01', 123456, 1),('2020-02-01', 123456, 1),
('2020-01-01', 123456, 1),
('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),('2019-10-01', 123456, 1),
('2019-08-01', 123456, 1),('2019-08-01', 123456, 1);

with result as (
  select count(p.id) as counter, yr as year, mth as month
  from temp_months tm
  left join my_table p
    on month(created_date)=tm.mth
    and year(created_date)=tm.yr
  group by yr, mth
  order by yr desc, mth desc
)
select
  case when counter = 0 then NULL else counter end as counter,
  year, month
from result;

Records: 12  Duplicates: 0  Warnings: 0

Records: 16  Duplicates: 0  Warnings: 0

counter	year	month
null	2020	6
1	2020	5
null	2020	4
null	2020	3
3	2020	2
1	2020	1
null	2019	12
null	2019	11
9	2019	10
null	2019	9
2	2019	8
null	2019	7