Php 合并具有相同id的sql行，求和并更新总数

我试图编写一个php脚本来比较数据库中的行，然后添加产品id匹配的数量。基于cusotmer_id

例如：

mydb.cart

id, customer_id, cart_id, product_id, qty, price

1, 0001000, 4545453, 20, 10, 12.99
2, 0001000, 7473432, 20, 2, 12.99

Result
3, 0001000, 7473432, 20, 12, 25.98

正在尝试合并上一个会话中的购物车信息

如有任何建议，我们将不胜感激

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谢谢

您可以用SQL而不是PHP来完成这项工作。更新新的购物车行并删除旧的购物车行。不确定这是否是正确的MySQL语法，但应该如下所示：

UPDATE cart SET qty = (
    SELECT SUM(qty) FROM cart c WHERE c.id = id 
    GROUP BY c.customer_id, c.product_id)
  WHERE EXISTS (
    SELECT 'x' FROM cart c2 
    WHERE c1.customer_id = c2.customer_id
    AND c1.product_id = c2.product_id
    AND c1.id < id);

DELETE FROM cart c1 WHERE EXISTS (
    SELECT 'x' FROM cart c2 
    WHERE c1.customer_id = c2.customer_id
    AND c1.product_id = c2.product_id
    AND c1.id < id);

UPDATE cart SET qty = (
    SELECT SUM(qty) FROM cart c WHERE c.id = id 
    GROUP BY c.customer_id, c.product_id)
  WHERE EXISTS (
    SELECT 'x' FROM cart c2 
    WHERE c1.customer_id = c2.customer_id
    AND c1.product_id = c2.product_id
    AND c1.id < id);

DELETE FROM cart c1 WHERE EXISTS (
    SELECT 'x' FROM cart c2 
    WHERE c1.customer_id = c2.customer_id
    AND c1.product_id = c2.product_id
    AND c1.id < id);