SQL Server 2019

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CREATE TABLE tablename
    ([pkProduct] int, [fkProductID] int, [intMajorIssue] int, [intMinorIssue] int)
;
    
INSERT INTO tablename
    ([pkProduct], [fkProductID], [intMajorIssue], [intMinorIssue])
VALUES
    (1, 10, 1, 0),
    (2, 10, 2, 0),
    (3, 10, 2, 1),
    (4, 10, 2, 1),
    (5, 10, 2, 2),
    (6, 11, 1, 0),
    (7, 11, 1, 1),
    (8, 11, 1, 1),
    (9, 11, 1, 1),
    (10, 11, 2, 0),
    (11, 11, 2, 1),
    (12, 12, 1, 0),
    (13, 12, 2, 1)
;
13 rows affected

with cte as (
  select *,
    row_number() over (partition by fkProductID, intMajorIssue order by pkProduct) rn
  from tablename  
)
update cte
set intMinorIssue = rn - 1
13 rows affected

select * from tablename


pkProduct
fkProductID
intMajorIssue
intMinorIssue


1
10
1
0

2
10
2
0

3
10
2
1

4
10
2
2

5
10
2
3

6
11
1
0

7
11
1
1

8
11
1
2

9
11
1
3

10
11
2
0

11
11
2
1

12
12
1
0

13
12
2
0

pkProduct	fkProductID	intMajorIssue	intMinorIssue
1	10	1	0
2	10	2	0
3	10	2	1
4	10	2	2
5	10	2	3
6	11	1	0
7	11	1	1
8	11	1	2
9	11	1	3
10	11	2	0
11	11	2	1
12	12	1	0
13	12	2	0

pkProduct	fkProductID	intMajorIssue	intMinorIssue
1	10	1	0
2	10	2	0
3	10	2	1
4	10	2	2
5	10	2	3
6	11	1	0
7	11	1	1
8	11	1	2
9	11	1	3
10	11	2	0
11	11	2	1
12	12	1	0
13	12	2	0

pkProduct	fkProductID	intMajorIssue	intMinorIssue
1	10	1	0
2	10	2	0
3	10	2	1
4	10	2	2
5	10	2	3
6	11	1	0
7	11	1	1
8	11	1	2
9	11	1	3
10	11	2	0
11	11	2	1
12	12	1	0
13	12	2	0