Question

在新的tupple插入到detail_of_sale表中之后，我想用触发器更新我的产品表。

我已经搜索了这个问题，并尝试了几种解决方法，但我无法解决。

这是我的桌子。

detail_of_sale（detailID，saleID，productID，quantity ...）

product（productID，stock ...）;

Create Trigger editQuantity AFTER INSERT ON detail_of_sale
BEGIN
Update product join detail_of_sale on
detail_of_sale.productID=product.productID set stock=stock-(Select quantity
from detail_of_sale where saleID=new.SaleID);
END

Answer 1

您不希望使用join，而只引用new表：

Update product 
    set stock = stock - new.quantity
    where productID = new.productID;

Answer 2

尝试一下：

    <?php
use Illuminate\Support\Facades\DB;
$my_id = \Session::get('user_id');
$messagesSentByMe = DB::table('messages')->where('sender_id', '=', $my_id)->get();
$messagesReceivedByMe = DB::table('messages')->where('receiver_id', '=', $my_id)->get();

//And the thing I wanna do is: extract similar id from the first messages, then the second messages and then from both the messages so that, I can have the user_id whom I have sent or received messages with.
?>

通过使用JOIN两个表来执行SQLLite更新语句

2 个答案: