SQL code to add missing StartDate between 2 dates in SQL Server - sql

Question

I have the below table ordered by clientID, contractID and effectiveDate. One Client has multiple contractID and it's respective effectiveDate.
the desired output is as below, where the new FYStartDate column should add the missing FYStartDate between 2 dates of subsequent contractIDs of a clientID(in this scenario, Fiscal Year starts on 01June of every year)
I would be appreciate if you could share the required SQL code.
I'm attaching the SQL code to generate the first table
CREATE TABLE [client] (
[clientid] [int] NULL,
[contractid] [int] NULL,
[effectivedate] [date] NULL
) ON [PRIMARY]
GO
insert into [client] values
('228','2','6/1/2003'),('228','136','6/1/2004'),('228','242','6/1/2008'),
('228','337','12/1/2012'),('228','584','6/1/2017'),('14216','319','5/1/2013'),
('14216','355','6/1/2013'),('14216','739','6/1/2020'),('14216','10','3/1/2021'),
('14216','1009','6/1/2021')

Answer 1

This is a bit convoluted without as #MatBailie suggest about having more structured data. To accomplish what you ask, each record needs to know when the contract before it and after it comes into effect. I think you need to play with the ordering because I didn't quite get how to order the results... by clientid, contractid, dates, etc?
UPDATED: see comments. Changed some CTEs, JOINS and ORDER BY for better partitioning by clientid.
CREATE TABLE [client] (
[clientid] [int] NULL,
[contractid] [int] NULL,
[effectivedate] [date] NULL
) ON [PRIMARY]
;
insert into [client] values
('228','2','6/1/2003'),('228','136','6/1/2004'),('228','242','6/1/2008'),
('228','337','12/1/2012'),('228','584','6/1/2017'),('14216','319','5/1/2013'),
('14216','355','6/1/2013'),('14216','739','6/1/2020'),('14216','10','3/1/2021'),
('14216','1009','6/1/2021')
;
--Need a sequence of numbers to create a sequence of fiscal years.
WITH x AS (
SELECT * FROM (VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) as x(a)
), y as (
SELECT ROW_NUMBER() OVER(ORDER BY tens.a, ones.a) as row_num
FROM x as ones, x as tens
), fiscYears as (
SELECT
fyStart = DATEFROMPARTS(2000 + y.row_num -1, 6, 1)
, fyEnd = DATEFROMPARTS(2000 + y.row_num, 5, 31)
FROM y
--Need to order the client records by effective date.
--From updated question... looks like we are reporting by clientid.
), clientOrd as (
SELECT c2.*, ROW_NUMBER() OVER(PARTITION BY c2.clientid ORDER BY c2.effectivedate) as row_num
FROM client c2
--For each contract, get the previous and next contracts by effective date.
), clientWNext as (
SELECT c.*
, cNext.effectivedate as nextEffectiveDate
, cPrev.effectivedate as prevEffectiveDate
FROM clientOrd as c
LEFT JOIN clientOrd as cNext
ON cNext.clientid = c.clientid
AND cNext.row_num = c.row_num + 1
LEFT JOIN clientOrd as cPrev
ON cPrev.clientid = c.clientid
AND cPrev.row_num = c.row_num - 1
)
SELECT
c.clientid
, cwn.contractid
, CASE WHEN cwn.effectiveDate >= fy.fyStart AND cwn.effectiveDate <= fy.fyEnd
THEN cwn.effectivedate
ELSE null
END as effectivedate
, fy.fyStart
FROM fiscYears as fy
--To get a full FY range for each client, we join to a distinct list of clients.
JOIN (
SELECT DISTINCT clientid FROM client
) as c
ON 1=1
--Need to join the list of contracts.
INNER JOIN clientWNext as cwn
ON cwn.clientid = c.clientid
--This is the main join criteria where the effective date is within the fy year start/end.
AND ((
cwn.effectivedate >= fy.fyStart
AND cwn.effectivedate <= fy.fyEnd
)
--This is the "alternate" join criteria where the previous contrat is still in effect
--but there is no new contract to supercede the previous.
OR (
cwn.prevEffectiveDate < fy.fyStart
AND cwn.effectiveDate < fy.fyStart
AND (cwn.nextEffectiveDate > fy.fyEnd OR cwn.nextEffectiveDate IS NULL)
))
--Limiting fiscal year date range.
WHERE fy.fyStart >= '1/1/2003'
AND fy.fyStart < '1/1/2024'
ORDER BY c.clientid, fy.fyStart, cwn.effectivedate
clientid
contractid
effectivedate
fyStart
228
2
2003-06-01
2003-06-01
228
136
2004-06-01
2004-06-01
228
136
null
2005-06-01
228
136
null
2006-06-01
228
136
null
2007-06-01
228
242
2008-06-01
2008-06-01
228
242
null
2009-06-01
228
242
null
2010-06-01
228
242
null
2011-06-01
228
337
2012-12-01
2012-06-01
228
337
null
2013-06-01
228
337
null
2014-06-01
228
337
null
2015-06-01
228
337
null
2016-06-01
228
584
2017-06-01
2017-06-01
228
584
null
2018-06-01
228
584
null
2019-06-01
228
584
null
2020-06-01
228
584
null
2021-06-01
228
584
null
2022-06-01
228
584
null
2023-06-01
14216
319
2013-05-01
2012-06-01
14216
355
2013-06-01
2013-06-01
14216
355
null
2014-06-01
14216
355
null
2015-06-01
14216
355
null
2016-06-01
14216
355
null
2017-06-01
14216
355
null
2018-06-01
14216
355
null
2019-06-01
14216
739
2020-06-01
2020-06-01
14216
10
2021-03-01
2020-06-01
14216
1009
2021-06-01
2021-06-01
14216
1009
null
2022-06-01
14216
1009
null
2023-06-01
fiddle