Obtener Trimestre

/*

select * from sp_obtener_trimestre(7);

select * from sp_obtener_trimestre(11);

select * from sp_obtener_trimestre(3);

*/

create or replace function sp_obtener_trimestre(p_num_mes int)
returns int
as $$
declare
    v_trim int = 1;
begin
    if(p_num_mes = 1 or p_num_mes = 2 or p_num_mes = 3)then
        return 1;
    end if;

    if(p_num_mes = 4 or p_num_mes = 5 or p_num_mes = 6)then
        return 2;
    end if;

    if(p_num_mes = 7 or p_num_mes = 8 or p_num_mes = 9)then
        return 3;
    end if;

    if(p_num_mes = 10 or p_num_mes = 11 or p_num_mes = 12)then
        return 4;
    end if;
end;
$$ language plpgsql;