Loop through table and update records - sql-server

Question

I need to modify a table based on multiple fields in that same table, and i can't seem to get it right and it is becomming a real pain.
My table looks like this:
Id person code product item delivery
41 254252 1368 prodname 561352401 23
41 254252 1368 prodname 4421252401 23
42 254252 1368 prodname 2501552403 23
42 254252 1368 prodname 5281352400 23
45 254251 1368 prodname 561352401 56
46 254251 1368 prodname 2501552403 56
49 254250 1368 prodname 561352401 69
50 254250 1368 prodname 2501552403 69
1357 253288 1368 prodname 4421252401 2
1358 253288 1368 prodname 5281352400 2
1359 253288 1368 prodname 9990070900 2
1377 253263 1220 prodname 2331252400 11
1378 253263 1220 prodname 2461252403 11
1379 253263 1220 prodname 9990070900 11
I need to update the delivery column based on: person, code and product. When the value in one of these column changes it should set it's counter to 0.
I need the output to look like this:
Id person code product item delivery
41 254252 1368 prodname 561352401 23
41 254252 1368 prodname 4421252401 24
42 254252 1368 prodname 2501552403 25
42 254252 1368 prodname 5281352400 26
45 254251 1368 prodname 561352401 56
46 254251 1368 prodname 2501552403 57
49 254250 1368 prodname 561352401 69
50 254250 1368 prodname 2501552403 70
1357 253288 1368 prodname 4421252401 2
1358 253288 1368 prodname 5281352400 3
1359 253288 1368 prodname 9990070900 4
1377 253263 1220 prodname 2331252400 11
1378 253263 1220 prodname 2461252403 12
1379 253263 1220 prodname 9990070900 13
So far i have this:
DECLARE #Id INT
DECLARE #person INT
DECLARE #code VARCHAR(15)
DECLARE #product VARCHAR(10)
DECLARE #Itemtype VARCHAR(10)
DECLARE #Item VARCHAR(50)
DECLARE #Delivery INT
DECLARE sel_cursor CURSOR FOR
SELECT Id, person, code, product, delivery FROM [dbo].[orders]
WHERE Itemtype = 'ART'
ORDER BY person, product,Itemtype, Item, delivery desc
DECLARE #Counter INT
OPEN sel_cursor
set #Counter = 0
FETCH NEXT FROM sel_cursor
INTO #Id, #person, #code, #product, #Delivery
WHILE ##FETCH_STATUS = 0
BEGIN
--WHILE (SELECT COUNT(*) FROM orders WHERE person=#person AND code=#code and product=#product) > 0
BEGIN
UPDATE Orders
SET delivery = (delivery + #Counter) WHERE person=#person AND code=#code AND product=#product
set #Counter = #Counter + 1
END
FETCH NEXT FROM sel_cursor
INTO #Id, #person, #code, #product, #Delivery
set #Counter = 0
END
CLOSE sel_cursor
DEALLOCATE sel_cursor
END

Answer 1

DECLARE #t TABLE (
Id INT,
person INT,
code VARCHAR(10),
product VARCHAR(20),
item VARCHAR(20),
delivery INT
)
INSERT INTO #t
VALUES
(41 , 254252, 1368, 'prodname', '561352401 ', 23),
(41 , 254252, 1368, 'prodname', '4421252401', 23),
(42 , 254252, 1368, 'prodname', '2501552403', 23),
(42 , 254252, 1368, 'prodname', '5281352400', 23),
(45 , 254251, 1368, 'prodname', '561352401 ', 56),
(46 , 254251, 1368, 'prodname', '2501552403', 56),
(49 , 254250, 1368, 'prodname', '561352401 ', 69),
(50 , 254250, 1368, 'prodname', '2501552403', 69),
(1357, 253288, 1368, 'prodname', '4421252401', 2 ),
(1358, 253288, 1368, 'prodname', '5281352400', 2 ),
(1359, 253288, 1368, 'prodname', '9990070900', 2 ),
(1377, 253263, 1220, 'prodname', '2331252400', 11),
(1378, 253263, 1220, 'prodname', '2461252403', 11),
(1379, 253263, 1220, 'prodname', '9990070900', 11)
;WITH cte AS
(
SELECT *, RowNum = ROW_NUMBER() OVER (
PARTITION BY Person, Code, product
ORDER BY 1/0) - 1
FROM #t
)
UPDATE cte
SET delivery += RowNum
SELECT * FROM #t
Output -
Id person code product item delivery
----------- ----------- ---------- ---------- ------------- -----------
41 254252 1368 prodname 561352401 23
41 254252 1368 prodname 4421252401 24
42 254252 1368 prodname 2501552403 25
42 254252 1368 prodname 5281352400 26
45 254251 1368 prodname 561352401 56
46 254251 1368 prodname 2501552403 57
49 254250 1368 prodname 561352401 69
50 254250 1368 prodname 2501552403 70
1357 253288 1368 prodname 4421252401 2
1358 253288 1368 prodname 5281352400 3
1359 253288 1368 prodname 9990070900 4
1377 253263 1220 prodname 2331252400 11
1378 253263 1220 prodname 2461252403 12
1379 253263 1220 prodname 9990070900 13