Update rows starting for specific number - sql

Question

I have a number into variable like:
DECLARE #CurrentLastFolio INT = (SELECT TOP 1 Folio FROM myTable ORDER BY folio DESC)
So supposing we have number 1004 into this variable.
Into another query I have some rows with folio = 0:
SELECT * FROM myTable WHERE folio = 0
That I want to do is to update this records with #CurrentLastFolio + 1 on each row. So first row should have Folio = 1005, next 1006 and so on.
How can I achieve that?

Answer 1

You can use the following solution, updating the variable on the UPDATE too:
DECLARE #CurrentLastFolio INT = (SELECT MAX(folio) FROM table_name);
UPDATE table_name
SET folio = #CurrentLastFolio, #CurrentLastFolio += 1
WHERE folio = 0
demo on dbfiddle.uk
Arithmetic overflow error converting expression to data type int:
In case your values get larger than 2,147,483,647 (maximum value of INT data type) you need to use BIGINT intead of INT to store (column folio) or increment the value (variable #CurrentLastFolio):
-- you need to use BIGINT on the table.
CREATE TABLE table_name (
folio BIGINT
)
-- you need to use BIGINT on the variable.
DECLARE #CurrentLastFolio BIGINT = (SELECT MAX(folio) from table_name);
-- now you can count and store numbers larger than INT maximum value.
UPDATE table_name
SET folio = #CurrentLastFolio, #CurrentLastFolio += 1
WHERE folio = 0
demo on dbfiddle.uk

Answer 2

Check this:
declare #CurrentLastFolio int = (SELECT TOP 1 Folio from myTable order by folio desc);
with tbl AS
(
SELECT * ,ROW_NUMBER() OVER( order by c1 ) AS rn
FROM myTable
)
update tbl set folio = rn + #x
Example Implementation for easy understanding
create table t (c1 int);
GO
✓
insert into t values (1), (2), (3)
GO
3 rows affected
declare #x int = 1000;
with tbl AS
(
SELECT * ,ROW_NUMBER() OVER( order by c1 ) AS rn
FROM t
)
update tbl set c1 = rn + #x
GO
3 rows affected
select * from t
GO
| c1 |
| ---: |
| 1001 |
| 1002 |
| 1003 |
db<>fiddle here