将查询合并为一个

Question

我希望一旦我将产品添加到“订单”table，产品的数量就会减少 1。我写了两个单独的查询来实现这个任务。

向“订单”添加数据的查询table:

INSERT INTO orders(id_buyer, id_product, date, status) 
VALUES (2, 8, '2022-05-22', 1);

请求将“数量”减一：

update products 
set amount = amount - 1, 
amount = amount - 1 
where id in ( select id_product from orders where status = 1);

是否可以将这两个查询合并为一个？

Answer 1

在回答问题时（即使这是否正确）您可以使用 AFTER INSERT TRIGGER

尝试：

CREATE TRIGGER after_orders_insert AFTER INSERT ON orders 
FOR EACH ROW
  UPDATE products
     SET amount=amount - 1
   WHERE id = NEW.id_product
   AND NEW.status =1;

Working demo

将查询合并为一个

Combine queries into one

mysql