use an
integers table:
create table integers ( i integer )
insert into integers values ( 1 )
insert into integers values ( 2 )
insert into integers values ( 3)
insert into integers values ( 4)
insert into integers values ( 5)
insert into integers values ( 6)
insert into integers values ( 7)
insert into integers values ( 8)
insert into integers values ( 9)
insert into integers values ( 10 )
insert into integers values ( 11 )
insert into integers values ( 12 )
then use a LEFT join from the integers to your data using i to match the month number
PHP Code:
select i as month
, Count(Messages.Id) as CountOfId
from integers
left outer
join Messages
on i = Month(DateMessages)
and Year(DateMessages) = 2004
inner
join List_Members_3
on Messages.Id = List_Members_3.Id
group
by i