带有子查询的MySQL条件UPDATE

Question

What I am trying to achieve is the following: update an existing table where each row has field "order-id" (incremented sequentially from 0). Now, if a row is deleted I want to ensure consistency of "order-id", ie starting from 0, incremented by 1. Example: Rows with order-id 0,1,2,3 - then row with order-id "2" gets deleted. I am looking for the SQL-statement that makes sure the order is not "0,1,3", but "0,1,2" ordered by the existing order-id (hence the ORDER BY in the subequery)

Here's what I have so far - works, but doesn't take ORDER BY into account for some reason

UPDATE walklist_walks AS w, 
   (SELECT walk_id, order_id,@n := -1 
   FROM walklist_walks 
   WHERE walklist=8 
   ORDER BY order_id ASC) m
SET w.order_id = @n := @n + 1
WHERE w.walklist = 8 
AND w.walk_id=m.walk_id

Here's some sample data:

   ROW 1: "walk_id 1059, order_id 0, walklist 8", 
   ROW 2: "walk_id 821, order_id 399, walklist 8", 
   ROW 3: "walk_id 91, order_id 45, walklist 8" 

After running the query this should look like

   ROW 1: "walk_id 1059, order_id 0, walklist 8", 
   ROW 2: "walk_id 91, order_id 1, walklist 8", 
   ROW 3: "walk_id 821, order_id 2, walklist 8"

Answer 1

What if you convert it to a update-join construct like

UPDATE walklist_walks AS w JOIN 
   (SELECT walk_id, order_id,@n := -1 
   FROM walklist_walks 
   WHERE walklist=8 
   ORDER BY order_id ASC) m ON w.walk_id=m.walk_id
SET w.order_id = @n := @n + 1
WHERE w.walklist = 8;