[英]Can someone help me implement the following trigger in PL/SQL Oracle?
So,所以,
I have 4 tables:我有4张桌子:
Suppliers( id_sup, name, city)
Products (id_prod, name, city)
Companies (id_co, name, city)
Deliveries (id_sup, id_prod, id_co)
I need a trigger so that if I want to update the city of a Supplier, I am not allowed if that supplier has a delivery where the product it delivers and the company it delivers to have the same city as it.我需要一个触发器,以便如果我想更新供应商的城市,如果该供应商的交货地点与其交付的产品和交付的公司具有相同的城市,则不允许我这样做。
This is what I've tried so far, but it's not working:这是我迄今为止尝试过的,但它不起作用:
CREATE OR REPLACE TRIGGER secure_suppliers
BEFORE UPDATE ON Suppliers
BEGIN
IF UPDATING ('city') THEN
IF (suppliers.id_sup IN (SELECT id_sup FROM Deliveries) AND suppliers.city = (Select p.city From Products p INNER JOIN Deliveries d ON (p.id_prod = d.id_prod)) AND suppliers.city = (Select c.city From Companies c INNER JOIN Deliveries d ON (c.id_co = d.id_co))) THEN
RAISE_APPLICATION_ERROR(-20500, 'Can't update city!');
End if;
End;
You can use one query to find if product
, supplier
and company
are in one city with new value of the supplier
then proceed with error handling in the trigger
as following:您可以使用一个查询来查找
product
、 supplier
和company
是否在一个城市中,并使用supplier
新值,然后在trigger
进行错误处理,如下所示:
CREATE OR REPLACE TRIGGER secure_suppliers
For each row -- row level trigger
BEFORE UPDATE OF city ON Suppliers -- trigger will execute on update of column city only
DECLARE
cnt NUMBER := 0;
BEGIN
select count(1)
Into cnt
From deliveries d
Join companies c on d.id_co = c.id_co
Join products p on d.id_prod = p.id_prod
Where p.city = c.city
And p.city = :new.city;
If cnt > 0 then
RAISE_APPLICATION_ERROR(-20500, 'Can''t update city!');
End if;
End;
/
Cheers!!干杯!!
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