select count(l.customer_code) as last_month, l.year,l.month
from zz_store_activity_by_month t, zz_store_activity_by_month l
where
t.customer_code = l.customer_code and
t.year * 12 + t.month = l.year * 12 + l.month - 1
group by l.year ,l.month
order by l.year desc ,l.month desc;
select count(customer_code) as this_month, year,month
from zz_store_activity_by_month
group by year,month
order by year desc ,month desc;
-----------------------------------------------------------
select count(l.customer_code) as last_month,
count(x.customer_code) as this_month,
l.year,
l.month
from zz_store_activity_by_month t,
zz_store_activity_by_month l,
zz_store_activity_by_month x
where
t.customer_code = l.customer_code and
t.year * 12 + t.month = l.year * 12 + l.month - 1 and
t.year = x.year and
t.month = x.month and
t.customer_code = x.customer_code
group by l.year ,l.month
order by l.year desc ,l.month desc;
137 137 2008 2
129 129 2008 1
148 148 2007 12
156 156 2007 11
...
..
.