Splitting a multi year contract row into multiple rows covering 1 year/365 days from start to end date - sql

Question

I have contract no 1 covering from 8/1/2022 to 7/31/2024, I need all the active contracts to split into multiple rows covering 365 days/year per row.
Existing table - EX- contract 1 is from 8/1/2022 to 7/31/2024,
I need contract 1 to be split from 8/1/2022 to 7/31/2023 in row1 and in ro2 contract 1 to be split from 8/1/2023 to 7/31/2024(2nd year of contract) like wise third year in row3 from 8/1/2024 to 7/31/2025.
Contract
start_date
End_date
1
8/1/2022
7/31/2024
23
8/7/2022
8/8/2023
26
6/8/2022
6/9/2025
I need above table to split like
S.No
Contract
start_date
End_date
1
1
8/1/2022
7/31/2023
2
1
8/1/2023
7/31/2024
3
23
8/7/2022
8/8/2023
4
26
6/8/2022
6/7/2023
5
26
6/8/2023
6/7/2024
6
26
6/8/2024
6/7/2025

Answer 1

The following will determine the maximum possible years for any contract, generate a sequence of numbers 0..N, calculate each potential full-year for each contract, and then trim the results to reflect the actual contract end-date.
-- Upper bound on number of years
DECLARE #MaxYears INT = (
SELECT 1 + MAX(DATEDIFF(year, Start_date, End_date))
FROM COntracts
)
;WITH NumTable AS (
SELECT 0 AS N
UNION ALL
SELECT N + 1
FROM NumTable
WHERE N < #Maxyears
)
SELECT
C.Contract,
D.Start_Date,
CASE WHEN D.End_date < C.End_date THEN D.End_date ELSE C.End_date END AS End_date
FROM Contracts C
CROSS APPLY (
SELECT
DATEADD(year, N.N, C.Start_date) AS Start_date,
DATEADD(day, -1, DATEADD(year, N.N + 1, C.Start_date)) AS End_date
FROM NumTable N
) D
WHERE D.Start_date <= C.End_date
ORDER BY C.Contract, D.Start_Date
If using SQL Server 2022, the NumTable CTE can be replaced with a GENERATE_SERIES() function, and the CASE expression can be replaced with LEAST().
SELECT C.Contract, D.Start_Date, LEAST(D.End_date, C.End_date) AS End_date
FROM Contracts C
CROSS APPLY (
SELECT
DATEADD(year, S.Value, C.Start_date) AS Start_date,
DATEADD(day, -1, DATEADD(year, S.Value + 1, C.Start_date)) AS End_date
FROM GENERATE_SERIES(0, DATEDIFF(year, C.Start_date, C.End_date)) S
) D
WHERE D.Start_date <= C.End_date
ORDER BY C.Contract, D.Start_Date
Results:
Contract
Start_Date
End_date
1
2022-08-01
2023-07-31
1
2023-08-01
2024-07-31
23
2022-08-07
2023-08-06
23
2023-08-07
2023-08-08
26
2022-06-08
2023-06-07
26
2023-06-08
2024-06-07
26
2024-06-08
2025-06-07
26
2025-06-08
2025-06-09
The above is slightly different from OP requested results, but I believe this to be correct based on the stated requirements.
See this db<>fiddle.
Edge case: If a contract starts on 29 February of a leap year, the calculations will define the start if each following year as either the 28th or 29th with a potential for a later contract year having a 366 day period from 28 February through 28 February of a later leap year.

Answer 2

You may try the following recursive CTE:
with cte as
(
select Contract, start_date sd, end_date ed, DATEADD(year, 1, start_date) new_ed
from table_name
where end_date >= GETDATE() -- get only active contracts
union all
select Contract, new_ed, ed, DATEADD(year, 1, new_ed)
from cte
where new_ed < DATEADD(day, -1, ed)
)
select ROW_NUMBER() over (order by Contract, sd) [S.No],
Contract,
sd start_date,
iif(YEAR(ed) = YEAR(new_ed), ed, DATEADD(day, -1, new_ed)) end_date
from cte
order by Contract, sd
See demo