How to generate records based on preceding rows value change/version history using SQL Server (TSQL)

Question

I have a table where I need to maintain record versioning based on records insertion and update on per day basis. The "RecordVersion" table looks like below:

VersionID    RecordID   RecordValue   DateID (FK Calendar)
---------   --------   -----------   ------
    1         R1          50           1
    2         R2          60           1
    3         R3          100          2
    4         R2          80           2
    5         R3          150          5
    6         R4          200          5

And the "Calendar" table looks like:

DateID      Date
------      --------
  1         1-May-19
  2         2-May-19
  3         3-May-19
  4         4-May-19
  5         5-May-19
  6         6-May-19

How RecordVersion table is getting populated:

1. On 1-May-19, Record R1 and R2 got inserted
2. On 2-May-19, a new Record R3 got inserted and exiting R2 updated (R1 remained unchanged). So for both new "insert" and "update" operations new version numbers were generated
3. On 3-May-19 and 4-May-19 no changes were made no version records were generated
4. On 5-May-19 again there were another new "Insert" and "Update" so two version were crated

Output(VersionHistory) should be like below:

DateID     VersionID   RecordID  RecordValue
1           1          R1          50  --Initial Record
1           2          R2          60
2           1          R1          50  -- Non Versioned
2           4          R2          80  -- Versioned for Update (50>80)
2           3          R3          100 -- New Insert
3           1          R1          50  |
3           4          R2          80  --- No Change -- Just Replicate Prev.
3           3          R3          100 |
4           1          R1          50  |
4           4          R2          80  --- No Change -- Just Replicate Prev.
4           3          R3          100 |
5           1          R1          50  -- Non Versioned
5           4          R2          80  -- Non Versioned
5           5          R3          150 -- Versioned for Update (100>150) 
5           6          R4          200 -- New Insert

It would be great if someone could generate the above output using TSQL. My SQLServer version is :

Microsoft SQL Azure (RTM) - 12.0.2000.8

Answer 1

That's my initial data:

DECLARE @RecordVersion TABLE (VersionID INT, RecordID VARCHAR(5), RecordValue INT, DateID INT);
INSERT INTO @RecordVersion(VersionID,RecordID,RecordValue,DateID)VALUES
     (1,'R1',50,1)
    ,(2,'R2',60,1)
    ,(3,'R3',100,2)
    ,(4,'R2',80,2)
    ,(5,'R3',150,5)
    ,(6,'R4',200,5)
;
DECLARE @Calendar TABLE (DateID INT, [Date] DATE);
INSERT INTO @Calendar (DateID,[Date])VALUES
     (1,'2019-05-01')
    ,(2,'2019-05-02')
    ,(3,'2019-05-03')
    ,(4,'2019-05-04')
    ,(5,'2019-05-05')
    ,(6,'2019-05-06')
;

The code:

SELECT b.DateID,b.VersionID,b.RecordID,b.RecordValue
FROM (
    SELECT c.DateID,a.VersionID,a.RecordID,a.RecordValue
        ,ROW_NUMBER()OVER(PARTITION BY c.DateID,a.RecordID ORDER BY a.DateID DESC) AS [rn]
    FROM @Calendar c
    INNER JOIN (
        SELECT v.DateID,d.[Date],v.VersionID,v.RecordID,v.RecordValue
        FROM @RecordVersion v
        INNER JOIN @Calendar d ON d.DateID = v.DateID
    ) a ON a.[Date] <= c.[Date]
) b
WHERE b.rn = 1
ORDER BY b.DateID,b.VersionID
;

However it returns date 6 as well, not sure if it's okay or not. Please let me know.