Calculating payment breakages - sql-server-2008

Question

I'm currently working on a report to highlight payment breakages, this is based on a customer paying in June, but then failing to pay in July.
I've currently got it set up to do an except query, to check one month and compare it to the next. Similar to below(syntax my not be correct as I have had to edit certain data).
DECLARE #StartDatePaid AS DATETIME
DECLARE #EndDatePaid AS DATETIME
DECLARE #StartDateMissed AS DATETIME
DECLARE #EndDateMissed AS DATETIME
SET #StartDatePaid = '01-Oct-2013'
SET #EndDatePaid = '31-Oct-2013'
SET #StartDateMissed = '01-Nov-2013'
SET #EndDateMissed = '05-Dec-2013'
SELECT d.StoreNo
, d.CustNo
FROM (
--Paid Range
SELECT c.CustNo, m.StoreNo
FROM dbo.tblCont AS c INNER JOIN
dbo.tblContDep AS cd ON c.ContractNo = cd.ContractNo INNER JOIN
dbo.tblCust AS m ON c.CustNo = m.CustNo INNER JOIN
dbo.tblTrans AS mx ON m.CustNo = mx.CustNo AND cd.AgendaCode = mx.AgendaCode INNER JOIN
dbo.tblCalender AS cl ON mx.DateEvent = cl.Date
WHERE (cd.Payment > 0) AND (m.Closed <> 'Y') AND (cd.AgendaCode <> 'OPCLIPMT')
AND mx.DateEvent BETWEEN #StartDatePaid AND #EndDatePaid
GROUP BY c.CustNo, m.StoreNo, mx.DateEvent
EXCEPT
--Missed Range
SELECT c.CustNo, m.StoreNo
FROM dbo.tblCont AS c INNER JOIN
dbo.tblContDep AS cd ON c.ContractNo = cd.ContractNo INNER JOIN
dbo.tblCust AS m ON c.CustNo = m.CustNo INNER JOIN
dbo.tblTrans AS mx ON m.CustNo = mx.CustNo AND cd.AgendaCode = mx.AgendaCode INNER JOIN
dtLookups.dbo.tblCalender AS cl ON mx.DateEvent = cl.Date
WHERE (cd.Payment > 0) AND (m.Closed <> 'Y') AND (cd.AgendaCode <> 'OPCLIPMT') AND (mx.DateEvent BETWEEN #StartDateMissed AND #EndDateMissed )
GROUP BY c.CustNo, m.StoreNo, mx.DateEvent
) AS d
WHERE d.StoreNo IN (72, 114, 121, 139, 185, 241, 266)
GROUP BY
d.StoreNo, d.CustNo
I will be switching it over to be based on calendar months instead of date ranges, my question is how am I best generating several months of breakages at once. To get a month on Month comparison at once, as it is I can only get it to create one months breakages based on supplied data.
Example of desired output
Month| breakges
June | 201
July | 189
Aug | 250
Open to suggestions on best practice also or ways to improve.

Answer 1

I admit I don't understand your query. Assuming your breakage is the first occurrence of missing payment, not the subsequent ones. You can produce the desired output like this:
-- prepare your source data
with cte1 as
(
select
user_id,
date, -- representing month by the first day
missed -- bool flag if payment was missed in that month
from ...
)
-- add a sequence number to the source data ordered by date
with cte2 as
(
select *,
row_number() over(partition by user_id order by date) rn
from cte1
)
-- select those records where payment was missed but the previous was ok
,cte3 as
(
select user_id, date from cte2 a
where a.missed = 1
and exists (
select * from cte2 b
where b.missed = 0
and b.uid = a.uid
and b.rn = a.rn -1
)
)
select date, count(*) as breakage from cte3 group by date