mysql double 触发两个一起更新

Question

尝试在 invoices 表中创建新触发器以UPDATE `invoices` SET invoices.`owes` = (`owes` - `paid`);

我得到一个错误，因为我已经在 payments 中更新了另一个触发器。 (见下文)

我希望将现有触发器保留在下方，但如何修改它以将 owes 也更新为 (owes - paid)在 invoices 表中。

CREATE TRIGGER `after_payment_update` AFTER UPDATE 
   ON `payments`
     FOR EACH ROW UPDATE `invoices` 
     SET invoices.`paid` = (SELECT SUM(payments .`payment`) 
   FROM payments WHERE payments.`invoice` = invoices.`invoice`)

Answer 1

您不能创建第二个触发器来“触发”与另一个触发器相同的操作。相反，您可以使用如下所示的 DELIMITER $$ 语句，并用您要执行的所有相关代码填充您的触发器。

DELIMITER $$
CREATE TRIGGER after_update_payments
AFTER UPDATE ON payments
FOR EACH ROW BEGIN
UPDATE invoices
     SET NEW.paid = (SELECT SUM(payment) FROM payments WHERE invoice = NEW.invoice),
         NEW.owes = (owes -(SELECT SUM(payment) FROM payments WHERE invoice = NEW.invoice));
END $$
DELIMITER ;

在上面的触发器中你实际上不需要 DELIMITER，所以我将向你展示一个你需要使用它的例子:

DELIMITER $$
CREATE TRIGGER after_update_payments
AFTER UPDATE ON payments
FOR EACH ROW BEGIN
  IF (some condition here) THEN
    UPDATE invoices
         SET NEW.paid = (SELECT SUM(payment) FROM payments WHERE invoice = NEW.invoice),
           NEW.owes = (owes -(SELECT SUM(payment) FROM payments WHERE invoice = NEW.invoice));
  END IF;
END $$
DELIMITER ;

作为一般规则，如果您需要执行多个需要 ; 结尾的语句，则需要使用 DELIMITER。如果这仍然没有意义，可以找到对定界符的很好解释 here .

现在，顺便提一下，我不认为这种方法是最最佳的方法。在你的情况下我会做的是创建一个组合这些表的 View 。例如:

CREATE 
ALGORITHM = UNDEFINED 
DEFINER = `root`@`localhost` 
SQL SECURITY DEFINER
VIEW invoice_payments_view AS (

    SELECT 
    t1.*,
    SUM(t2.payment) as amount_paid,
    SUM(t2.owes - SUM(t2.payment)) as amount_owed
    FROM invoices t1
    JOIN payments t2 ON (t1.invoice=t2.invoice)
    GROUP BY t1.invoice
)

然后要访问 amount_paid 和 amount_owed 列，您只需查询以下内容:

SELECT invoice, amount_paid, amount_owed FROM invoice_payments_view 
WHERE invoice=1;

请注意，我绝不是该主题的专家，我只是向您展示我将如何处理这种情况。另外，我没有测试任何这段代码，所以您可能需要稍微修改一下。如果您有任何问题，请告诉我，我可以更新。