SQL Server 2019

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE Product (
  "Id" INTEGER,
  "InvoicesStr" VARCHAR(max)
);

INSERT INTO Product
  ("Id", "InvoicesStr")
VALUES
  ('1', '4,5,6,7,34,6,78,967,3,534,'),
  ('2', '454,767,344,567,89676,4435,3,434,');
2 rows affected

UPDATE Product
SET InvoicesStr.WRITE('100,', NULL, NULL)
WHERE Id = 2;
1 rows affected

SELECT * FROM Product


Id
InvoicesStr


1
4,5,6,7,34,6,78,967,3,534,

2
454,767,344,567,89676,4435,3,434,100,

Id	InvoicesStr
1	4,5,6,7,34,6,78,967,3,534,
2	454,767,344,567,89676,4435,3,434,100,