MySQL 5.7

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create table Ejemplo(Cod_prod int, Mes int, `Año` int);
insert into Ejemplo(Cod_prod, `Año`, Mes) values (1, 2021, 1), (1, 2020, 12), (1, 2020, 11); 
insert into Ejemplo(Cod_prod, `Año`, Mes) values (2, 2021, 2), (2, 2021, 1), (2, 2020, 12); 
select *,
       year(m.fecha_filtro) as mes_filtro,
       month(m.fecha_filtro) as year_filtro
       from Ejemplo e
       inner join (select DATE_ADD("2021-03-20", INTERVAL 0 MONTH) as fecha_filtro union
                   select DATE_ADD("2021-03-20", INTERVAL -1 MONTH) union 
                   select DATE_ADD("2021-03-20", INTERVAL -2 MONTH)) m
             on 1 = 1

       order by Cod_prod, year_filtro, mes_filtro;


Cod_prod
Mes
Año
fecha_filtro
mes_filtro
year_filtro


1
1
2021
2021-01-20
2021
1

1
11
2020
2021-01-20
2021
1

1
12
2020
2021-01-20
2021
1

1
11
2020
2021-02-20
2021
2

1
12
2020
2021-02-20
2021
2

1
1
2021
2021-02-20
2021
2

1
12
2020
2021-03-20
2021
3

1
1
2021
2021-03-20
2021
3

1
11
2020
2021-03-20
2021
3

2
2
2021
2021-01-20
2021
1

2
12
2020
2021-01-20
2021
1

2
1
2021
2021-01-20
2021
1

2
12
2020
2021-02-20
2021
2

2
1
2021
2021-02-20
2021
2

2
2
2021
2021-02-20
2021
2

2
1
2021
2021-03-20
2021
3

2
2
2021
2021-03-20
2021
3

2
12
2020
2021-03-20
2021
3


select e.*
       from Ejemplo e
       inner join (select DATE_ADD("2021-03-20", INTERVAL  0 MONTH) as fecha_filtro union
                   select DATE_ADD("2021-03-20", INTERVAL -1 MONTH) union 
                   select DATE_ADD("2021-03-20", INTERVAL -2 MONTH)) m
             on year(m.fecha_filtro) = e.`Año`
             and month(m.fecha_filtro) = e.Mes

       ;


Cod_prod
Mes
Año


1
1
2021

2
2
2021

2
1
2021

Cod_prod	Mes	Año	fecha_filtro	mes_filtro	year_filtro
1	1	2021	2021-01-20	2021	1
1	11	2020	2021-01-20	2021	1
1	12	2020	2021-01-20	2021	1
1	11	2020	2021-02-20	2021	2
1	12	2020	2021-02-20	2021	2
1	1	2021	2021-02-20	2021	2
1	12	2020	2021-03-20	2021	3
1	1	2021	2021-03-20	2021	3
1	11	2020	2021-03-20	2021	3
2	2	2021	2021-01-20	2021	1
2	12	2020	2021-01-20	2021	1
2	1	2021	2021-01-20	2021	1
2	12	2020	2021-02-20	2021	2
2	1	2021	2021-02-20	2021	2
2	2	2021	2021-02-20	2021	2
2	1	2021	2021-03-20	2021	3
2	2	2021	2021-03-20	2021	3
2	12	2020	2021-03-20	2021	3