触发将消息覆盖为错误 (ORA-02292)

Question

我想覆盖产生错误的消息 (ORA-02292)。 就是这样的消息

ORA-02292: integrity constraint (IVANKA.FK_SUPPLIER) violated - child record found

我想要一个触发器来覆盖上面的消息到他的例子中（我的覆盖:)）

我试过这样做

第一次建表

CREATE TABLE supplier
( supplier_id numeric(10) not null,
  supplier_name varchar2(50) not null,
  contact_name varchar2(50),
  CONSTRAINT supplier_pk PRIMARY KEY (supplier_id)
);

CREATE TABLE products
( product_id numeric(10) not null,
  supplier_id numeric(10) not null,
  CONSTRAINT fk_supplier
    FOREIGN KEY (supplier_id)
    REFERENCES supplier (supplier_id)
);

然后插入数据

INSERT INTO supplier
(supplier_id, supplier_name, contact_name)
VALUES (1000, 'Microsoft', 'Bill Gates');

INSERT INTO products
(product_id, supplier_id)
VALUES (50000, 1000);

然后触发

create or replace trigger  sup_z 
after delete on supplier
for each row
declare 
v_error_constraint exception;
  pragma exception_init(v_error_constraint, -2292);
begin
     null;
exception
      When v_error_constraint then
      raise_application_error(-20001, 
         'My ovvervide:)');
End;  

然后执行删除以生成消息

DELETE from supplier
WHERE supplier_id = 1000

但我在触发器中看不到我的消息我看到了

   ORA-02292: integrity constraint (IVANKA.FK_SUPPLIER) violated - child record found

你能帮帮我吗？我做错了什么？

Answer 1

当您只需要要打印的消息时，为什么我们首先需要触发器？我们不应该只处理一个例外吗？

declare 
    v_error_constraint exception;
    pragma exception_init(v_error_constraint, -2292);
begin
     DELETE from supplier
     WHERE supplier_id = 1000;
exception
      When v_error_constraint then
      raise_application_error(-20001, 
         'My ovvervide:)');
End;

Answer 2

您的触发器在DELETE 完成后触发，因此如果DELETE 出现错误，它将永远不会触发。 如果您发现一些子记录，您可以使用BEFORE 触发器来避免DELETE；例如：

create or replace trigger  sup_z 
before delete on supplier
for each row
declare 
  vNumberOfChild number;
begin
     select count(1)
     into vNumberOfChild
     from products
     where  supplier_id = :old.supplier_id;
     --
     if vNumberOfChild > 0 then
        raise_application_error(-20001, 'My ovveride:)');
     end if;
End;  

另一种方法是定义处理删除的过程：

SQL> create or replace procedure deleteSupplier(p_id in numeric) is
  2  vNumberOfChild number;
  3  begin
  4       select count(1)
  5       into vNumberOfChild
  6       from products
  7       where  supplier_id = p_id;
  8       --
  9       if vNumberOfChild > 0 then
 10          dbms_output.put_line('My ovveride');
 11       else
 12          delete supplier
 13          where supplier_id = p_id;
 14       end if;
 15  end;
 16  /

Procedure created.

SQL> set serveroutput on
SQL> exec deleteSupplier(1000);
My ovveride

PL/SQL procedure successfully completed.

这避免了运行delete之前检查数据，因此您不需要触发器。

Answer 3

检查this（当违反 PL/SQL 约束时显示自定义消息）。我想你想要类似的东西。