How to COUNT rows according to specific complicated rules? - sql

Question

I have the following table:
custid custname channelid channel dateViewed
--------------------------------------------------------------
1 A 1 ABSS 2016-01-09
2 B 2 STHHG 2016-01-19
3 C 4 XGGTS 2016-01-09
6 D 4 XGGTS 2016-01-09
2 B 2 STHHG 2016-01-26
2 B 2 STHHG 2016-01-28
1 A 3 SSJ 2016-01-28
1 A 1 ABSS 2016-01-28
2 B 2 STHHG 2016-02-02
2 B 7 UUJKS 2016-02-10
2 B 8 AKKDC 2016-02-10
2 B 9 GGSK 2016-02-10
2 B 9 GGSK 2016-02-11
2 B 7 UUJKS 2016-02-27
And I want the results to be:
custid custname month count
------------------------------
1 A 1 1
2 B 1 1
2 B 2 4
3 C 1 1
6 D 1 1
According to the following rules:
All channel views subscription is billed every 15 days. If the
customer viewed the same channel within the 15 days, he will only be
billed once for that channel. For instance, custid 2, custname B his billing cycle is 19 Jan - 3 Feb (one billing cycle), 4 Feb - 20 Feb (one billing cycle) and so on. Therefore, he is billed only 1 time in Jan since he watch the same channel throughout the billing cycle; and he is billed 4 times in Feb for watching (channelid 7, 8, 9) and channelid 7 watched on 27 Feb (since this falls in another billing cycle, customer B is also charged here). Customer B is not charged on 2 Feb for watching channel 2 since he was already billed in 19 jan - 3 Feb billing cycle.
An invoice is generated every month for each customer, therefore, the
results should show the 'Month' and the 'Count' of the channels
viewed for each customer.
Can this be done in SQL server?

Answer 1

;WITH cte AS (
SELECT custid,
custname,
channelid,
channel,
dateViewed,
CAST(DATEADD(day,15,dateViewed) as date) as dateEnd,
ROW_NUMBER() OVER (PARTITION BY custid, channelid ORDER BY dateViewed) AS rn
FROM (VALUES
(1, 'A', 1, 'ABSS', '2016-01-09'),(2, 'B', 2, 'STHHG', '2016-01-19'),
(3, 'C', 4, 'XGGTS', '2016-01-09'),(6, 'D', 4, 'XGGTS', '2016-01-09'),
(2, 'B', 2, 'STHHG', '2016-01-26'),(2, 'B', 2, 'STHHG', '2016-01-28'),
(1, 'A', 3, 'SSJ', '2016-01-28'),(1, 'A', 1, 'ABSS', '2016-01-28'),
(2, 'B', 2, 'STHHG', '2016-02-02'),(2, 'B', 7, 'UUJKS', '2016-02-10'),
(2, 'B', 8, 'AKKDC', '2016-02-10'),(2, 'B', 9, 'GGSK', '2016-02-10'),
(2, 'B', 9, 'GGSK', '2016-02-11'),(2, 'B', 7, 'UUJKS', '2016-02-27')
) as t(custid, custname, channelid, channel, dateViewed)
), res AS (
SELECT custid, channelid, dateViewed, dateEnd, 1 as Lev
FROM cte
WHERE rn = 1
UNION ALL
SELECT c.custid, c.channelid, c.dateViewed, c.dateEnd, lev + 1
FROM res r
INNER JOIN cte c ON c.dateViewed > r.dateEnd and c.custid = r.custid and c.channelid = r.channelid
), final AS (
SELECT * ,
ROW_NUMBER() OVER (PARTITION BY custid, channelid, lev ORDER BY dateViewed) rn,
DENSE_RANK() OVER (ORDER BY custid, channelid, dateEnd) dr
FROM res
)
SELECT b.custid,
b.custname,
MONTH(f.dateViewed) as [month],
COUNT(distinct dr) as [count]
FROM cte b
LEFT JOIN final f
ON b.channelid = f.channelid and b.custid = f.custid and b.dateViewed between f.dateViewed and f.dateEnd
WHERE f.rn = 1
GROUP BY b.custid,
b.custname,
MONTH(f.dateViewed)
Output:
custid custname month count
----------- -------- ----------- -----------
1 A 1 3
2 B 1 1
2 B 2 4
3 C 1 1
6 D 1 1
(5 row(s) affected)
I don't know why you get 1 in count field for customer A. He got:
ABSS 2016-01-09 +1 to count (+15 days = 2016-01-24)
SSJ 2016-01-28 +1 to count
ABSS 2016-01-28 +1 to count (28-01 > 24.01)
So in January there must be count = 3.

Answer 2

Whenever I am trying to count things with complex criteria, I use a sum and case statement. Something like below:
SELECT custid, custname,
SUM(CASE WHEN somecriteria
THEN 1
ELSE 0
END) As CriteriaCount
FROM whateverTable
GROUP BY custid, custname
You can make that somecriteria variable as complicated a statement as you like, so long as it returns a boolean. If it passes, this row returns a 1. If it fails, the row reutrns a 0, then we sum up the values returned to get the count.

Answer 3

Generally this is how you can get any number (10 in this example) of fixed 15 day intervals starting at the given date (#dd in this example).
DECLARE #dd date = CAST('2016-01-19 17:30' AS DATE);
WITH E1(N) AS (
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1),
E2(N) AS (SELECT 1 FROM E1 a, E1 b),
E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10,000 rows max
tally(N) AS (SELECT TOP (10) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4)
SELECT
startd = DATEADD(D,(N-1)*15, #dd),
endd = DATEADD(D, N*15-1, #dd)
FROM tally
Adapt it to the rules defining how start date must be calculated for the user (and probably chanel).

Answer 4

#Sturgus what if I want to define it in the code? Any other
alternatives besides defining it in the table? How to write a query
that can be run every month to generate the monthly invoice. –
saturday 15 mins ago
Well, one way or another, you will have to save each customer's billing start date (minimally). If you want to do this entirely in SQL without 'editing the database', something like the following should work. The drawback to this approach is that you would need to manually edit the "INSERT INTO" statement every month to suit your needs. If you were allowed to edit the already existing customers table or create a new one, then it would reduce this manual effort.
DECLARE #CustomerBillingPeriodsTVP AS Table(
custID int UNIQUE,
BillingCycleID int,
BillingStartDate Date,
BillingEndDate Date
);
INSERT INTO #CustomerBillingPeriodsTVP (custID, BillingCycleID, BillingStartDate, BillingEndDate) VALUES
(1, 1, '2016-01-03', '2016-01-18'), (2, 1, '2016-01-18', '2016-02-03'), (3, 1, '2016-01-15', '2016-01-30'), (6, 1, '2016-01-14', '2016-01-29');
SELECT A.custid, A.custname, B.BillingCycleID AS [month], COUNT(DISTINCT A.channelid) AS [count]
FROM dbo.tblCustomerChannelViews AS A INNER JOIN #CustomerBillingPeriodsTVP AS B ON A.custid = B.CustID
GROUP BY A.custid, A.custname, B.BillingCycleID;
GO
Where are you getting your customers' billing start dates as it is?

Answer 5

I'm not sure how this solution will scale - but with some good index candidates and decent data housekeeping, it'll work..
You're going to need some extra info for starters, and to normalize your data. You will need to know the first charging period start date for each customer. So store that in a customer table.
Here are the tables I used:
create table #channelViews
(
custId int, channelId int, viewDate datetime
)
create table #channel
(
channelId int, channelName varchar(max)
)
create table #customer
(
custId int, custname varchar(max), chargingStartDate datetime
)
I'll populate some data. I won't get the same results as your sample output, because I don't have the appropriate start dates for each customer. Customer 2 will be OK though.
insert into #channel (channelId, channelName)
select 1, 'ABSS'
union select 2, 'STHHG'
union select 4, 'XGGTS'
union select 3, 'SSJ'
union select 7, 'UUJKS'
union select 8, 'AKKDC'
union select 9, 'GGSK'
insert into #customer (custId, custname, chargingStartDate)
select 1, 'A', '4 Jan 2016'
union select 2, 'B', '19 Jan 2016'
union select 3, 'C', '5 Jan 2016'
union select 6, 'D', '5 Jan 2016'
insert into #channelViews (custId, channelId, viewDate)
select 1,1,'2016-01-09'
union select 2,2,'2016-01-19'
union select 3,4,'2016-01-09'
union select 6,4,'2016-01-09'
union select 2,2,'2016-01-26'
union select 2,2,'2016-01-28'
union select 1,3,'2016-01-28'
union select 1,1,'2016-01-28'
union select 2,2,'2016-02-02'
union select 2,7,'2016-02-10'
union select 2,8,'2016-02-10'
union select 2,9,'2016-02-10'
union select 2,9,'2016-02-11'
union select 2,7,'2016-02-27'
And here is the somewhat unweildy query, in a single statement.
The two underlying sub-queries are actually the same data, so there may be more appropriate / efficient ways to generate these.
We need to exclude from billing any channel charged in the same charging period C for the previous Month. This is the essence of the join. I used a right-join so that I could exclude all such matches from the results (using old.custId is null).
select c.custId, c.[custname], [month], count(*) [count] from
(
select new.custId, new.channelId, new.month, new.chargingPeriod
from
(
select distinct cv.custId, cv.channelId, month(viewdate) [month], (convert(int, cv.viewDate) - convert(int, c.chargingStartDate))/15 chargingPeriod
from #channelViews cv join #customer c on cv.custId = c.custId
) old
right join
(
select distinct cv.custId, cv.channelId, month(viewdate) [month], (convert(int, cv.viewDate) - convert(int, c.chargingStartDate))/15 chargingPeriod
from #channelViews cv join #customer c on cv.custId = c.custId
) new
on old.custId = new.custId
and old.channelId = new.channelId
and old.month = new.Month -1
and old.chargingPeriod = new.chargingPeriod
where old.custId is null
group by new.custId, new.month, new.chargingPeriod, new.channelId
) filteredResults
join #customer c on c.custId = filteredResults.custId
group by c.custId, [month], c.custname
order by c.custId, [month], c.custname
And finally my results:
custId custname month count
1 A 1 3
2 B 1 1
2 B 2 4
3 C 1 1
6 D 1 1
This query does the same thing:
select c.custId, c.custname, [month], count(*) from
(
select cv.custId, min(month(viewdate)) [month], cv.channelId
from #channelViews cv join #customer c on cv.custId = c.custId
group by cv.custId, cv.channelId, (convert(int, cv.viewDate) - convert(int, c.chargingStartDate))/15
) x
join #customer c
on c.custId = x.custId
group by c.custId, c.custname, x.[month]
order by custId, [month]