Question

Hello guys.

I've an issue with a simple query.
Here we go, that's the code.

UPDATE user_resources AS ures
                LEFT JOIN user_buildings as ub
                ON ub.city_id = ures.city_id
                INNER JOIN building_consumption AS bcons
                ON bcons.resource_id = ures.resource_id
                SET ures.quantity = ures.quantity - abs(FORMULA HERE that requires 
         building level and consumption at lvl 1 [default])
                    WHERE
                (SELECT COUNT(id) FROM building_consumption AS bc2
 WHERE bc2.building_id=ub.building_id)  =
                    (SELECT COUNT(bc3.id) FROM building_consumption AS bc3
                      LEFT JOIN  tmp_user_resources AS ures
                        ON ures.resource_id = bc3.resource_id
                    WHERE ures.city_id = ub.city_id
                          AND bc3.building_id=ub.building_id
                          AND bc3.quantity>0
                          AND IFNULL(ures.quantity, 0) - abs(FORMULA AGAIN);

I'll try to explain a bit.

As you can imagine, this is for a game. Users (players) can has different buildings in different cities.

tab user_buildings

|id, city_id, buildings_id, level, usage|

A building can produce different resources tab building_production

|id, building_id, resource_id, quantity_h|

but it can consume some resources too: tab building_consumption

|id, building_id, resource_id, quantity_h|

Obviously a building cannot produce if there are not enough resources to consume for his job. That's why I'm trying to compare WHERE SELECT COUNT how many resources it has to consume AND how many resources it can actually consume.

Mysql does NOT ALLOW to subquery same table inside an UPDATE stmt.

Using a cursor + loop is too much slow. I prefer to use different solution.

Temp table could be a solution but my problem now is how to update the temp table without triggers? (UPDATE + SELECT fires triggers and to avoid endless loops mysql block the query, and i can't pause/resume triggers because

  IF ((@TRIGGER_CHECKS = FALSE)
      OR (@TRIGGER_BEFORE_INSERT_CHECKS = FALSE))
    AND (USER() = 'root@localhost')
  THEN
    LEAVE thisTrigger;
  END IF;

is inside the trigger itself).

I am open to all your suggestions!
Thanks

P.S. The code must be inside a scheduled event.

Mysql Update select subquery vs trigger loop

0 个答案: