SQL Server 2017

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SELECT 1  c INTO tab_name
1 rows affected

CREATE TABLE tab_stat(id INT IDENTITY(1,1), t DATETIME DEFAULT GETDATE(), cnt BIGINT);

INSERT INTO tab_stat(cnt)
SELECT COUNT(*)
FROM tab_name;

SELECT *, cnt - LAG(cnt,1,0) OVER(ORDER BY id) AS diff
FROM tab_stat
ORDER BY id DESC;


id
t
cnt
diff


1
2023-11-01 12:22:01.613
1
1


INSERT INTO tab_name
VALUES(1),(2),(3)
3 rows affected

INSERT INTO tab_stat(cnt)
SELECT COUNT(*)
FROM tab_name;

SELECT *, cnt - LAG(cnt,1,0) OVER(ORDER BY t) AS diff
FROM tab_stat
ORDER BY id DESC;


id
t
cnt
diff


2
2023-11-01 12:22:01.613
4
3

1
2023-11-01 12:22:01.613
1
1