Select top n percent by year - sql

Question

I have a query that I built that brings back net sales YTD up to the most recently completed month. The query unions totals from invoices and credit memos. It works great. I use the query in another tool that sums by cardcode and allows me to do interesting pivots and so forth. Here is that query:
select x.cardcode,
x.customer,
case
when x.rep is null then (select slpname from ocrd inner join oslp on ocrd.slpcode = oslp.slpcode where ocrd.cardcode = x.cardcode)
else
x.rep
end as rep,
x.city,
x.state,
x.country,
case
when isnumeric(x.total) = 0 then 0
else x.total
end as [net total],
x.docdate
from (
select t0.cardcode as cardcode,
t0.[cardname] as customer,
t1.city as city,
t1.state as state,
t1.country as country,
t4.slpname as rep,
sum(t3.linetotal) - t2.discsum as total,
t2.docdate as [docdate]
from ocrd t0
inner join crd1 t1 on (t0.cardcode = t1.cardcode and t0.shiptodef = t1.address)
left outer join oinv t2 on t0.cardcode = t2.cardcode
left outer join inv1 t3 on t2.docentry = t3.docentry
left outer join oslp t4 on t2.slpcode = t4.slpcode
where t0.[cardtype] = 'C' and
t1.adrestype = 'S'
group by t0.cardcode, t0.cardname, t1.city, t1.state, t1.country, t4.slpname, t2.discsum, t2.docdate
union all
select t0.cardcode as cardcode,
t0.cardname as customer,
t1.city as city,
t1.state as state,
t1.country as country,
t4.slpname as rep,
-1*(sum(t3.linetotal) - t2.discsum) as total,
t2.docdate
from ocrd t0
inner join crd1 t1 on (t0.cardcode = t1.cardcode and t0.shiptodef = t1.address)
left outer join orin t2 on t0.cardcode = t2.cardcode
left outer join rin1 t3 on t2.docentry = t3.docentry
left outer join oslp t4 on t2.slpcode = t4.slpcode
where t0.[cardtype] = 'C' and
t1.adrestype = 'S'
group by t0.cardcode,
t0.cardname,
t1.city,
t1.state,
t1.country,
t4.slpname,
t2.discsum,
t2.docdate) x
where (x.docdate between '2008/01/01' and dateadd(day, -1, '2008/' + cast(month(getdate()) as varchar(2)) + '/01')
or x.docdate between '2009/01/01' and dateadd(day, -1, '2009/' + cast(month(getdate()) as varchar(2)) + '/01')
or x.docdate between '2010/01/01' and dateadd(day, -1, '2010/' + cast(month(getdate()) as varchar(2)) + '/01'))
group by x.cardcode, x.customer, x.rep, x.city, x.state, x.country, x.total, x.docdate
Now, I want to modify the query to return the top n, say 20, percent of customer's net total for each year. This is where I am having trouble. I am using SQL Server so first I thought I would try using row_number() over(partition.... but I haven't got it quite right (I know its not right because I can check it against the report I am reverse engineering). Here is my first attempt:
select m.Cardcode, m.Customer, m.Rep, m.City, m.State, m.Country, m.Nettotal as 'Net Total', m.docdate as 'Posting Date'
from (
select t.cardcode, t.customer, t.rep, t.city, t.state, t.country, t.nettotal, t.docdate, row_number() over(partition by t.docdate order by t.nettotal desc) as rownum
from (
select x.cardcode,
x.customer,
case
when x.rep is null then (select slpname from ocrd inner join oslp on ocrd.slpcode = oslp.slpcode where ocrd.cardcode = x.cardcode)
else
x.rep
end as rep,
x.city,
x.state,
x.country,
case
when isnumeric(x.total) = 0 then 0
else x.total
end as nettotal,
x.docdate
from (
select t0.cardcode as cardcode,
t0.[cardname] as customer,
t1.city as city,
t1.state as state,
t1.country as country,
t4.slpname as rep,
sum(t3.linetotal) - t2.discsum as total,
t2.docdate as docdate
from ocrd t0
inner join crd1 t1 on (t0.cardcode = t1.cardcode and t0.shiptodef = t1.address)
left outer join oinv t2 on t0.cardcode = t2.cardcode
left outer join inv1 t3 on t2.docentry = t3.docentry
left outer join oslp t4 on t2.slpcode = t4.slpcode
where t0.[cardtype] = 'C' and
t1.adrestype = 'S'
group by t0.cardcode,
t0.cardname,
t1.city,
t1.state,
t1.country,
t4.slpname,
t2.discsum,
t2.docdate
union all
select t0.cardcode as cardcode,
t0.cardname as customer,
t1.city as city,
t1.country as country,
t1.state as state,
t4.slpname as rep,
-1*(sum(t3.linetotal) - t2.discsum) as total,
t2.docdate
from ocrd t0
inner join crd1 t1 on (t0.cardcode = t1.cardcode and t0.shiptodef = t1.address)
left outer join orin t2 on t0.cardcode = t2.cardcode
left outer join rin1 t3 on t2.docentry = t3.docentry
left outer join oslp t4 on t2.slpcode = t4.slpcode
where t0.[cardtype] = 'C' and
t1.adrestype = 'S'
group by t0.cardcode,
t0.cardname,
t1.city,
t1.state,
t1.country,
t4.slpname,
t2.discsum,
t2.docdate) x
where (x.docdate between '2008/01/01' and dateadd(day, -1, '2008/' + cast(month(getdate()) as varchar(2)) + '/01')
or x.docdate between '2009/01/01' and dateadd(day, -1, '2009/' + cast(month(getdate()) as varchar(2)) + '/01')
or x.docdate between '2010/01/01' and dateadd(day, -1, '2010/' + cast(month(getdate()) as varchar(2)) + '/01'))
group by x.cardcode,
x.customer,
x.rep,
x.city,
x.state,
x.country,
x.total,
x.docdate) as t
) as m
where rownum <= 20
Going down this road is troublesome even if I got it right because it doesn't allow me to get the top n percent, just the top n.
I have yet to try using cross apply or sub selects to achieve the result I desire.
Can someone help me get this right? Also, how it is written is probably not efficient and the hard coded date range selection is not a good solution. I guess there is a lot to improve :)
Your help is appreciated.

Answer 1

If you need a more individual percentage (let's say 17%) you can use row_number and count:
with cSalesPerYear as (
select s.Year, c.Customer,
RankNo = rank() over (partition by s.Year order by S.Amount desc),
RowNo = row_number() over (partition by s.Year order by S.Amount desc),
CountOrders = count() over (partition by s.Year)
from dbo.Customers c
inner join dbo.Sales s
on s.CustomerID = c.CustomerID
)
select *
from cSalesPerYear
where RowNo <= #Percentage * CountOrders
-- RankNo <= #Percentage * CountOrders --<-- "with ties" version

Answer 2

You can use one of the ranking functions in SQL Server - but not ROW_NUMBER() but NTILE() instead.
NTILE() will break up a result set into as many chunks of data that you specify - since you want to the top 20%, you'll probably use NTILE(5).
So your CTE should look something like this:
WITH CustomerPerYear AS
(
SELECT
c.Name, s.Sales,
NTILE(5) OVER (PARTITION BY c.CustomerID ORDER BY s.Amount DESC) as 'NTile'
FROM
dbo.Customer c
INNER JOIN
dbo.Sales s ON s.CustomerID = c.CustomerID
)
SELECT *
FROM CustomerPerYear
WHERE NTile = 1
So basically you're partioning your data by customer, and then you're ranking each customers' sales into 5 NTile groups ordered by the sales amount. The NTILE = 1 is the top 20% of your sales, for each customer.
See the MSDN docs on NTILE for more details, if needed.