SQL Server 2019

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create table Subscriptions
(	ID int primary key
,	CustomerID int not null
,	StartDate date not null
,	EndDate date not null
);
insert into Subscriptions 
  (ID, CustomerID, StartDate, EndDate)
values
 (1, 1, '2020-01-01', '2021-01-01')
,(2, 1, '2021-01-01', '2022-01-01') 
,(3, 1, '2022-01-01', '2023-01-01')
,(4, 2, '2021-01-01', '2022-01-01')
,(5, 3, '2020-01-01', '2021-01-01') 
,(6, 3, '2022-01-01', '2023-01-01')
,(7, 4, '2020-01-01', '2021-01-01')
,(8, 4, '2021-01-01', '2022-01-01') 
,(9, 4, '2022-01-01', '2023-01-01');
9 rows affected

select *
from Subscriptions
;


ID
CustomerID
StartDate
EndDate


1
1
2020-01-01
2021-01-01

2
1
2021-01-01
2022-01-01

3
1
2022-01-01
2023-01-01

4
2
2021-01-01
2022-01-01

5
3
2020-01-01
2021-01-01

6
3
2022-01-01
2023-01-01

7
4
2020-01-01
2021-01-01

8
4
2021-01-01
2022-01-01

9
4
2022-01-01
2023-01-01

ID	CustomerID	StartDate	EndDate
1	1	2020-01-01	2021-01-01
2	1	2021-01-01	2022-01-01
3	1	2022-01-01	2023-01-01
4	2	2021-01-01	2022-01-01
5	3	2020-01-01	2021-01-01
6	3	2022-01-01	2023-01-01
7	4	2020-01-01	2021-01-01
8	4	2021-01-01	2022-01-01
9	4	2022-01-01	2023-01-01