有人可以帮我在 PL/SQL Oracle 中实现以下触发器吗？

Question

所以，

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)

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位于与其相同的城市，则不允许我这样做。

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;

Answer 1

您可以使用一个查询来查找product、supplier 和company 是否在一个具有supplier 新值的城市中，然后继续在trigger 中进行错误处理，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;
/

干杯！！