如何在Laravel中从另一个表中减去一个表上的值

Question

I have two tables one called products and the other called orders.
Products as columns: id, plant_name, price, stock.
Orders as columns: id product_id, quantity.

When someone makes a order they pick a quantity. How do I reduce the quantity from the stock on the other table?

I am using controllers and elequent in Laravel if that helps.

Answer 1

This seems like a general implementation question?

It depends on how you process orders. If new ones are stored in a table and you're running a cron that goes through them, then loop the orders and update quantity one by one.

Ex:

 $newOrders = \DB::table('orders')->get();
 foreach ($newOrders as $order){
     $stock = \DB::table('products')->where('id', $order->product_id)->first()->stock;
     if($stock > $order->quantity){
         \DB::table('products')->where('id', $order->product_id)->decrement('stock',$order->quantity);
 }

If you process it on the fly in the controller, then skip the loop above and simply update the products table when you process the order..