SQL Server 2014

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-- Data table that I have
CREATE TABLE DataTable (
        Date Date,
        CapVersion varchar(100),
        CaseNumber int
    );
INSERT INTO DataTable (Date, CapVersion, CaseNumber)
VALUES 
('2020-12-02', 'CAP A', 1002),
('2020-12-02', 'CAP A', 1003),
('2020-12-02', 'CAP A', 1004),
--compare CAP A with CAP B
('2020-12-11', 'CAP B', 1002),
('2020-12-11', 'CAP B', 1003),
--compare CAP B with CAP C
('2020-12-14', 'CAP C', 1003),
('2020-12-14', 'CAP C', 1004),
('2020-12-14', 'CAP C', 1005),
--compare CAP C with CAP D
('2020-12-15', 'CAP D', 1005),
('2020-12-15', 'CAP D', 1007);

SELECT * FROM DataTable;

-- Result that I expected 
CREATE TABLE OutputTable(
        Date Date,
        CapVersion varchar(100),
        CaseNumberAdded int,
        CaseNumberRemoved int,
        CaseNumberExisiting int
    );
INSERT INTO OutputTable (Date,CapVersion,CaseNumberAdded,CaseNumberRemoved,CaseNumberExisiting)
VALUES 
('2020-12-02', 'CAP A', 0,0,3),
--compare CAP A with CAP B
('2020-12-11', 'CAP B', 0,1,2),
--compare CAP B with CAP C
('2020-12-14', 'CAP C', 2,1,1),
--compare CAP C with CAP D
('2020-12-14', 'CAP D', 1,2,1);

SELECT * FROM OutputTable;

Date	CapVersion	CaseNumber
2020-12-02	CAP A	1002
2020-12-02	CAP A	1003
2020-12-02	CAP A	1004
2020-12-11	CAP B	1002
2020-12-11	CAP B	1003
2020-12-14	CAP C	1003
2020-12-14	CAP C	1004
2020-12-14	CAP C	1005
2020-12-15	CAP D	1005
2020-12-15	CAP D	1007

Date	CapVersion	CaseNumberAdded	CaseNumberRemoved	CaseNumberExisiting
2020-12-02	CAP A	0	0	3
2020-12-11	CAP B	0	1	2
2020-12-14	CAP C	2	1	1
2020-12-14	CAP D	1	2	1

WITH 
BaseDate AS ( SELECT MIN(DataTable.Date) BaseDate
              FROM DataTable ),
Dates AS ( SELECT DISTINCT DataTable.Date, DataTable.CapVersion
              FROM DataTable ),
BaseData AS ( SELECT Dates.Date, DataTable.CapVersion, DataTable.CaseNumber
              FROM DataTable
              CROSS JOIN Dates
              JOIN BaseDate ON DataTable.Date = BaseDate.BaseDate ),
Detailed AS ( SELECT COALESCE(DataTable.Date, BaseData.Date) Date, 
                     COALESCE(DataTable.CaseNumber, BaseData.CaseNumber) CaseNumber,
                     CASE WHEN DataTable.CaseNumber IS NOT NULL AND BaseData.CaseNumber IS NULL
                          THEN 1
                          ELSE 0 END CaseNumberAdded,
                     CASE WHEN DataTable.CaseNumber IS NULL AND BaseData.CaseNumber IS NOT NULL
                          THEN 1
                          ELSE 0 END CaseNumberRemoved,
                     CASE WHEN DataTable.CaseNumber IS NOT NULL AND BaseData.CaseNumber IS NOT NULL
                          THEN 1
                          ELSE 0 END CaseNumberExisiting
              FROM BaseData
              FULL JOIN DataTable ON DataTable.CaseNumber = BaseData.CaseNumber
                                 AND DataTable.Date = BaseData.Date )
SELECT Detailed.Date,
       Dates.CapVersion,
       SUM(Detailed.CaseNumberAdded) CaseNumberAdded,
       SUM(Detailed.CaseNumberRemoved) CaseNumberRemoved,
       SUM(Detailed.CaseNumberExisiting) CaseNumberExisiting
FROM Detailed
JOIN Dates ON Detailed.Date = Dates.Date
GROUP BY Detailed.Date, Dates.CapVersion;

Date	CapVersion	CaseNumberAdded	CaseNumberRemoved	CaseNumberExisiting
2020-12-02	CAP A	0	0	3
2020-12-11	CAP B	0	1	2
2020-12-14	CAP C	1	1	2
2020-12-15	CAP D	2	3	0