使用MySQL触发器更新客户余额

Question

我需要一些帮助来理解触发器及其工作原理。我有3个表：

客户
ID |余额

发票
Id | Custid |金额

付款
Id | CustId |量

我有一个INSERT语句来插入发票：

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

和需要更新插入后客户的平衡。同样，插入或创建付款后。我需要从客户余额中扣除。

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

任何协助将不胜感激创造这些触发器。

Answer 1

你需要两个触发器 - 一个发票表：

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; 

和一个支付表：

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 ; 

fiddle here