使用 MySQL 触发器更新客户余额-数据库问题

Using MySQL triggers to update customers balance(使用 MySQL 触发器更新客户余额)

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问题描述

我需要一些帮助来理解触发器及其工作原理.我有 3 张桌子:

I need some help in understanding triggers and how they work. I have 3 tables:

客户
身份证 |余额

Customers
Id | Balance

发票
身份证 |客户 |金额

Invoices
Id | Custid | Amount

付款
身份证 |客户 ID |金额

Payments
Id | CustId | Amount

我有一个插入语句来插入发票:

I have an insert statement to insert the invoices:

$this->db->insert('invoices', array(
            'CustomerId' => $data['customerId'],
            'Description' => $data['Description'],
            'DateCreated' => $data['DateCreated'],
            'Amount' => $data['Amount']
        ));

并且需要在插入后更新客户余额.同样，在插入或创建付款之后.我需要从客户余额中扣除.

and need to update the customers balance after the insert. Similarly, after inserting or creating a payment. I need to deduct from the clients balance.

public function createPayment($data) {
        $this->db->insert('payments', array(
            'CustomerId' => $data['customerid'],
            'DateCreated' => date("Y-m-d H:i:s"),
            'Amount' => $data['amount']
        ));
    }

在创建这些触发器方面的任何帮助将不胜感激.

Any assistance would be appreciated in creating these triggers.

推荐答案

您需要两个触发器 - 一个用于发票表:

You'll need two triggers - one for the invoice table:

delimiter //
CREATE TRIGGER add_invoice_to_balance AFTER INSERT ON invoices
FOR EACH
ROW
BEGIN
    UPDATE Customers SET balance = balance + NEW.Amount
      WHERE Customers.id = NEW.custid;
END;
//
delimiter;

还有一个用于支付表:

delimiter //
CREATE TRIGGER add_payment_to_balance AFTER INSERT ON payments
FOR EACH
ROW
BEGIN
    UPDATE Customers SET balance = balance - NEW.Amount
      WHERE Customers.id = NEW.custid;
END;
//
delimiter ;

在这里小提琴

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