Determine which of four date ranges a single date range overlaps - sql-server

Question

I have Subscriptions that can last anywhere (as far as my output should be concerned) from 1 to 4 fiscal quarters (could also be seen as four date ranges)
I'm using Arizona Fiscal Quarters:
Q1: Jul 1st - Sep 30th
Q2: Oct 1st - Dec 31st
Q3: Jan 1st - Mar 31st
Q4: Apr 1st - Jun 30th
What I need to figure out is how many subscriptions are active in each quarter based on the subscriptions start and end dates.
For example, using (YYYY-MM-DD), I have:
A subscription that starts on 2016-07-06 and ends on 2017-02-22 I should be able to see I have a subscription active in Q1, Q2, and Q3.
Another subscription that starts on 2016-10-18 and ends on 2016-10-24 would only be seen as active for Q2
Finally, a subscription that starts on 2016-09-28 but has no end date would be seen as active for Q1, Q2, Q3, and Q4 (so whatever starting quarter all the way to Q4)
Below is my current SQL Server Script, and here it is on SQL Fiddle:
WITH SubscriptionInfo AS
(
SELECT
[Subscriptions].[Customer_Id]
,[DistributorTypes].[Name] AS [Distributor Type]
,[Customers].Zip_Id
,[Subscriptions].[UnsubscribeReason_Id]
,[Subscriptions].[Id] AS [Subscription ID]
,CONVERT(DATE, [Subscriptions].[StartDate]) AS [Subscription Start Date]
,CONVERT(DATE, [Subscriptions].[EndDate]) AS [Subscription End Date]
,[PriorityLevels].PriorityLevel AS [Priority Level]
,CONVERT(DATE, [SubscriptionPriorityLevels].StartDate) AS [Priority Level Start Date]
,CONVERT(DATE, [SubscriptionPriorityLevels].EndDate) AS [Priority Level End Date]
,[FundingSources].[Name] AS [Funding Source]
,CONVERT(DATE, [SubscriptionFundingSources].StartDate) AS [SubscriptionFundingSources Start Date]
,CONVERT(DATE, [SubscriptionFundingSources].EndDate) AS [SubscriptionFundingSources End Date]
FROM [Subscriptions]
LEFT JOIN [SubscriptionPriorityLevels]
ON [SubscriptionPriorityLevels].Subscription_Id = Subscriptions.Id
LEFT JOIN [PriorityLevels]
ON [PriorityLevels].Id = SubscriptionPriorityLevels.PriorityLevel_Id
LEFT JOIN [SubscriptionFundingSources]
ON [SubscriptionFundingSources].Subscription_Id = Subscriptions.Id
LEFT JOIN [FundingSources]
ON [FundingSources].Id = [SubscriptionFundingSources].FundingSource_Id
LEFT JOIN [Customers]
ON [Customers].Id = [Subscriptions].Customer_Id
LEFT JOIN [DistributorTypes]
ON [DistributorTypes].Id = Customers.DistributorType_Id
WHERE
([Subscriptions].StartDate >= '2016-07-01') -- Dummy dates, would later be parameters
AND ([Subscriptions].EndDate <= '2017-06-30'
OR [Subscriptions].EndDate IS NULL)
AND ([PriorityLevels].PriorityLevel IN (2, 3)) -- Only care about these two levels
AND ([Customers].DistributorType_Id = 1) -- Distributor Type: Number One Distrubition
AND ([SubscriptionFundingSources].FundingSource_Id = 2) -- Funding Source: First Bank
)
SELECT
[SubscriptionInfo].Customer_Id
,[SubscriptionInfo].[Subscription ID]
,MAX([SubscriptionInfo].[Priority Level]) AS [Highest Priority Level]
,CASE -- Determine which fiscal quarter each Subscription Start Date belongs to
WHEN MONTH([SubscriptionInfo].[Subscription Start Date]) IN (7, 8, 9) THEN 1 -- July, August, September
WHEN MONTH([SubscriptionInfo].[Subscription Start Date]) IN (10, 11, 12) THEN 2 -- October, November, December
WHEN MONTH([SubscriptionInfo].[Subscription Start Date]) IN (1, 2, 3) THEN 3 -- January, Feburary, March
ELSE 4 -- April, May, June
END AS [Fiscal Quarter Start Date]
,CASE -- Determine which fiscal quarter each Subscription Start Date belongs to
WHEN MONTH([SubscriptionInfo].[Subscription End Date]) IN (7, 8, 9) THEN 1 -- July, August, September
WHEN MONTH([SubscriptionInfo].[Subscription End Date]) IN (10, 11, 12) THEN 2 -- October, November, December
WHEN MONTH([SubscriptionInfo].[Subscription End Date]) IN (1, 2, 3) THEN 3 -- January, Feburary, March
ELSE 4 -- April, May, June
END AS [Fiscal Quarter End Date]
FROM [SubscriptionInfo]
GROUP BY
[SubscriptionInfo].Customer_Id
,[SubscriptionInfo].[Subscription ID]
,CASE -- Group Subscription Start Date's into Fiscal Quarters
WHEN MONTH([SubscriptionInfo].[Subscription Start Date]) IN (7, 8, 9) THEN 1 -- July, August, September
WHEN MONTH([SubscriptionInfo].[Subscription Start Date]) IN (10, 11, 12) THEN 2 -- October, November, December
WHEN MONTH([SubscriptionInfo].[Subscription Start Date]) IN (1, 2, 3) THEN 3 -- January, Feburary, March
ELSE 4 -- April, May, June
END
,CASE -- Group Subscription End Date's into Fiscal Quarters
WHEN MONTH([SubscriptionInfo].[Subscription End Date]) IN (7, 8, 9) THEN 1 -- July, August, September
WHEN MONTH([SubscriptionInfo].[Subscription End Date]) IN (10, 11, 12) THEN 2 -- October, November, December
WHEN MONTH([SubscriptionInfo].[Subscription End Date]) IN (1, 2, 3) THEN 3 -- January, Feburary, March
ELSE 4 -- April, May, June
END
ORDER BY
[SubscriptionInfo].Customer_Id
So far I'm able to identify in what fiscal quarter a subscription started and what fiscal quarter it ended.
I want to be able to count how many subscriptions were active in each quarter.
Desired Output:
| FirstQuarter | SecondQuarter | ThirdQuarter | FourthQuarter |
|--------------|---------------|--------------|---------------|
| 2 | 1 | 3 | 3 |

Answer 1

Once you have a table describing the quarters' start and end dates as #Sean Lange suggested, you just need to compare your subscriptions' start and end date to the quarters' start and end date and then count them up where they overlap. Basically, two ranges have some overlap if A.Start < B.End and A.End > B.Start.
Here's a complete example of the pattern.
-------------------------
-- construct the quarters table (taken from the SQL Fiddle in comments above)
DECLARE #FiscalDate Table
(
Id INT NOT NULL,
FiscalYear INT NOT NULL,
FiscalQuarter INT NOT NULL,
QuarterStartDate DATE NOT NULL,
QuarterEndDate DATE NOT NULL
PRIMARY KEY(Id)
);
INSERT INTO #FiscalDate
(Id, FiscalYear, FiscalQuarter, QuarterStartDate, QuarterEndDate)
VALUES
( 1, 2016, 1, '2016-07-01', '2016-09-30')
,(2, 2016, 2, '2016-10-01', '2016-12-31')
,(3, 2017, 3, '2017-01-01', '2017-03-31')
,(4, 2017, 4, '2017-04-01', '2017-06-30')
;
-------------------------
--Get some random test data to imitate subscriptions ranges
DECLARE #tempSet Table(a date, b date)
INSERT INTO #tempSet SELECT TOP 15
dateadd(dd, ROUND(365 * RAND(convert(varbinary, newid())), 0), '2016-07-01') as a
, dateadd(dd, ROUND(365 * RAND(convert(varbinary, newid())), 0), '2016-07-01') as b
FROM sysobjects
-------------------------
-- Fix our random data a little (start date needs to be before end date)
DECLARE #DateRanges Table(StartDate date, EndDate date)
INSERT INTO #DateRanges
SELECT a, b FROM #tempset WHERE a <= b UNION SELECT b, a FROM #tempset WHERE b < a
-------------------------
-- Show our Date ranges in a useful order for review
SELECT * FROM #DateRanges ORDER BY StartDate, EndDate
-------------------------
-- Show our by-quarter counts.
SELECT
fd.FiscalQuarter
, count(*) as ActiveSubsCount
FROM
#FiscalDate fd
JOIN
#DateRanges dr
on fd.QuarterStartDate < dr.EndDate
and fd.QuarterEndDate >= dr.StartDate
GROUP BY
fd.FiscalQuarter
-------------------------
-- and in your desired output (without your quarters table)
SELECT
COUNT(CASE WHEN '2016-07-01' < dr.EndDate AND '2016-09-30' >= dr.StartDate THEN 1 ELSE NULL END) AS FirstQuarter
, COUNT(CASE WHEN '2016-10-01' < dr.EndDate AND '2016-12-31' >= dr.StartDate THEN 1 ELSE NULL END) AS SecondQuarter
, COUNT(CASE WHEN '2017-01-01' < dr.EndDate AND '2017-03-31' >= dr.StartDate THEN 1 ELSE NULL END) AS ThirdQuarter
, COUNT(CASE WHEN '2017-04-01' < dr.EndDate AND '2017-06-30' >= dr.StartDate THEN 1 ELSE NULL END) AS FourthQuarter
FROM
#DateRanges dr