Mysql Update column with subrequest Order By - mysql

Question

I have a table biblek2 items with those 4 columns :
id (autoincrement)
catid(int)
introtext(varchar)
ordering(int)
Table biblek2_items
╔════╦═══════╦═══════════╦══════════╗
║ ID ║ catid ║ introtext ║ ordering ║
╠════╬═══════╬═══════════╬══════════╣
║ 1 ║ 3024 ║ orange ║ 122 ║
║ 2 ║ 2024 ║ zebra ║ 45 ║
║ 3 ║ 3010 ║ juice ║ 55 ║
║ 4 ║ 3002 ║ build ║ 17 ║
║ 5 ║ 2003 ║ car ║ 87 ║
║ 6 ║ 1610 ║ other ║ 1521 ║
║ 7 ║ 1620 ║ other ║ 200 ║
╚════╩═══════╩═══════════╩══════════╝
I expect that
Table biblek2_items
╔════╦═══════╦═══════════╦══════════╗
║ ID ║ catid ║ introtext ║ ordering ║
╠════╬═══════╬═══════════╬══════════╣
║ 5 ║ 2003 ║ car ║ 1 ║
║ 4 ║ 3002 ║ build ║ 2 ║
║ 3 ║ 3010 ║ juice ║ 3 ║
║ 1 ║ 3024 ║ orange ║ 4 ║
║ 2 ║ 2024 ║ zebra ║ 5 ║
╚════╩═══════╩═══════════╩══════════╝
I want to
select * from biblek2_items where catid between 2001 and 3024
ORDER BY introtext ASC
empty the ordering column
reorder the ordering column by increment from 1 to n according to the result of the order column
I tried this with no success
DECLARE #variable int
SET #variable = 0
UPDATE `biblek2_items`
SET #variable = ordering = #variable + 1
WHERE ordering IN (SELECT ordering
FROM `biblek2_items`
WHERE catid BETWEEN 2001 AND 3024
ORDER BY `introtext` DESC)
I read in the forum that MySQL can't allow subrequests with ORDER BY, so could you help me

Answer 1

As explained in the comments :
The ORDER BY in your sub query makes no sense anyway, because, you don't LIMIT. So all rows will be returned and it doesn't matter how they are ordered because all of them are taken into account with the IN in your main query.
But there are other issues with your query.
Do this instead :
SET #row_number = 0 ;
UPDATE biblek2_items,
(select id, catid,introtext,ordering, (#row_number:=#row_number + 1) AS newordering
from biblek2_items
where catid between 2001 and 3024
ORDER BY introtext ASC
) as temp
SET biblek2_items.ordering = temp.newordering
WHERE biblek2_items.ID = temp.ID
Additionally, if you have a large table, and a lot of users actively writing on it, to avoid inconsistencies or locking issues, I would suggest a slightly different method, using a temporary table to store the computed new ordering.
CREATE TABLE biblek2_items_TEMP (ID INT, ordering INT);
SET #row_number = 0 ;
INSERT INTO biblek2_items_TEMP
select id, (#row_number:=#row_number + 1) AS newordering
from biblek2_items
where catid between 2001 and 3024
ORDER BY introtext ASC
;
UPDATE biblek2_items, biblek2_items_TEMP
SET biblek2_items.ordering = biblek2_items_TEMP.ordering
WHERE biblek2_items.ID = biblek2_items_TEMP.ID;
DROP TABLE biblek2_items_TEMP;
Tested successfully on MySQL 5.7 and MariaDB 10