Updating order fields in table with MySQL

Dan Sosedoff — Thu, 05 Feb 2009 04:00:54 +0000

This is a simple piece of code which describing how to update special order field in table. For example, you have table ‘photos’:

+ --------------------------------- +
| ID    | UserID | OrderID | ImgURL |
+ --------------------------------- +
| 1132  | 1      | 0       | ...    |
| 2124  | 1      | 0       | ...    |
| 3456  | 1      | 0       | ...    |
.....................................
| N     | 1      | 0       | ...    |
+ --------------------------------- +

OrderID field value by default is 0. If some images has been deleted order lose its consistency.
To repair order we can use single transaction:

BEGIN;
 
SET @ORDER := 0;
UPDATE photos
SET order_id = (SELECT @ORDER := @ORDER + 1)
WHERE user_id = 1;
 
COMMIT;

After executing this on table ‘images’ we`ll get such result:

+ --------------------------------- +
| ID    | UserID | OrderID | ImgURL |
+ --------------------------------- +
| 1132  | 1      | 1       | ...    |
| 2124  | 1      | 2       | ...    |
| 3456  | 1      | 3       | ...    |
.....................................
| N     | 1      | M       | ...    |
+ --------------------------------- +

Some developers instead of using resources of mysql script language trying to solve this problem by executing numerous call, such ‘UPDATE table SET order_id = [value] WHERE id = [id] LIMIT 1;’. It`s wrong. MySQL language have a lot of ways to make it easy. At least UDF`s.

dan.thoughts » auto

Updating order fields in table with MySQL