Bring through previous 12 months count while grouping by period - sql

Question

I'm trying to use the below code to bring though a count of all lines in the last 12 month period for the period and plant, please see the output below.
So for example with the below output, rather than the 12 months column currently containing the total for the period, I want the count using a period between 201001-201101 (Please note, my example was only for the dataset below and the 12 months column needs to adapt for each period).
Period Plant Stock Special MonthTotal 12Months
201101 0EA0 27 0 27 27
201101 0EB0 35 2 37 37
The issue I'm having is that rather than bring through the last 12 month count, my code is merely bringing through the count for the current period. Please can someone assist?
select
convert(varchar(6),dateadd(mm,0,P.Dt),112) as Period,P.Plant,
Sum(Case When Left(Upper(Material),2) = 'ZZ' then 1 else 0 end) as Stock,
Sum(Case When Left(Upper(Material),2) <> 'ZZ' then 1 else 0 end) as Special
,Count(*) as MonthTotal,Sum(Case When
convert(varchar(6),dateadd(mm,0,P.Dt),112)
Between
convert(varchar(6),dateadd(mm,-12,P.Dt),112)
And
convert(varchar(6),dateadd(mm,0,P.Dt),112) Then 1 else 0 End
)as [12Months]
from
iesaonline.dbo.DS_POs as P where
Plant IN(
Select Client From METRICS.DBO.CO_001_Plants_090_Final
where CustGrp = 'Hovis'
)
Group by
P.Plant,convert(varchar(6),dateadd(mm,0,P.Dt),112)
order by
convert(varchar(6),dateadd(mm,0,Dt),112),Plant

Answer 1

The problem seems to be that you're grouping by year/month and trying to sum values outside that year/month range. Without sample data, I can't be certain, but it sounds like you want a rolling 12 month sum. Something like below should get you where you want to go.
;with monthlySubtotal as
(
select
dateadd(m, 1-datepart(day, p.dt), p.dt) as PeriodMonth
,P.Plant
,Sum(Case When Left(Upper(Material),2) = 'ZZ' then 1 else 0 end) as Stock
,Sum(Case When Left(Upper(Material),2) <> 'ZZ' then 1 else 0 end) as Special
,Count(*) as MonthTotal
from
iesaonline.dbo.DS_POs as P where
Plant IN(
Select Client From METRICS.DBO.CO_001_Plants_090_Final
where CustGrp = 'Hovis'
)
Group by
P.Plant
,dateadd(m, 1-datepart(day, p.dt), p.dt)
)
SELECT
convert(varchar(6),m1.PeriodMonth,112) Period
, m1.Plant
, m1.Stock
, m1.Special
, m1.MonthTotal
, SUM(m2.monthtotal) 12mototal
FROM monthlySubtotal m1
JOIN monthlySubtotal m2
ON m2.plant = m1.plant
AND m2.periodmonth BETWEEN dateadd(m, -11, m1.periodmonth)
AND m1.periodmonth
--You may want to filter this
--WHERE m1.periodmonth >= startdate
GROUP BY
convert(varchar(6),m1.PeriodMonth,112)
, m1.Plant
, m1.Stock
, m1.Special
, m1.MonthTotal
ORDER BY
Period
, Plant

Answer 2

There is no need to do everything at the same time.
It's easier to first get the monthly values
SELECT DATEADD(month, DATEDIFF(month, 0, Dt), 0) as FOM
, Plant
, Stock = SUM(CASE WHEN LEFT(Upper(Material), 2) = 'ZZ' THEN 1 ELSE 0 END)
, Special = SUM(CASE WHEN LEFT(Upper(Material), 2) = 'ZZ' THEN 0 ELSE 1 END)
FROM DS_POs
GROUP BY Plant, DATEADD(month, DATEDIFF(month, 0, Dt), 0)
and using that as the base to get the last 12 month of result using a CROSS APPLY
WITH DS_POSM AS (
SELECT DATEADD(month, DATEDIFF(month, 0, Dt), 0) as FOM
, Plant
, Stock = SUM(CASE WHEN LEFT(Upper(Material), 2) = 'ZZ' THEN 1 ELSE 0 END)
, Special = SUM(CASE WHEN LEFT(Upper(Material), 2) = 'ZZ' THEN 0 ELSE 1 END)
FROM DS_POs
GROUP BY Plant, DATEADD(month, DATEDIFF(month, 0, Dt), 0)
)
SELECT Convert(char(6), FOM, 112) Period
, Plant
, Stock
, Special
, MonthTotal = Stock + Special
, ly.[12Months]
FROM DS_POSM a
CROSS APPLY (SELECT Sum(Stock + Special) [12Months]
FROM DS_POSM lastyear
WHERE lastyear.FOM Between DateAdd(mm, -12, a.FOM) And a.FOM
AND lastyear.Plant = a.Plant
) ly
ORDER BY FOM, Plant
DATEADD(month, DATEDIFF(month, 0, Dt), 0) get the first day of the month of Dt