sql - Oracle SQL 触发器在实现时发生变异

Question

此触发器在执行插入或更新操作时遇到问题。但是，触发器的创建没有错误。目的是检查 invoice_total 是否大于 payment_total + credit_total 的总和。任何帮助将非常感激：

Create or Replace Trigger invoices_before_update_payment
Before Insert or Update On invoices
For Each Row
Declare
InvTotal Number;
t_payment Number;
t_credit Number;
Begin
select invoice_total, payment_total, credit_total
Into
InvTotal, t_payment, t_credit
From invoices
Where invoice_id = :New.invoice_id;
DBMS_OUTPUT.PUT_LINE(InvTotal);
If (InvTotal) < (t_payment + t_credit)
Then
Raise_application_error(-20005, 'Invoice total is larger than the credit total and payment total');
End if;
End;
/

Answer 1

您无法从触发器触发的表中进行选择，否则您会收到此错误。

为什么不简单地在触发器中使用 :new 值？

BEGIN
IF :new.invoice_total > :new.payment_total + :new.credit_total THEN

我根据错误消息语义反转了关系运算符。