更新后在 DML 触发器中调用对象成员函数（ORACLE 数据库）

Question

我有一个包含 table PRODUCTS 个对象 Product 的数据库，其中 PRIMARY KEY 是 EAN 字段。每次更新一行我都想调用新对象Product修改的成员函数。我制作了这个触发器：

CREATE OR REPLACE TRIGGER SHOW_PROFIT_PERCENTAGE
AFTER UPDATE ON PRODUCTS
FOR EACH ROW

DECLARE

P  Product;

BEGIN

    SELECT VALUE(PS) INTO P
    FROM PRODUCTS PS
    WHERE EAN = :NEW.EAN;

    DBMS_OUTPUT.PUT_LINE('Profit percentage: ' || P.getProfit());

END;

但是当我更新 PRODUCTS 时它给了我这个错误：

table PRODUCTS is mutating, trigger/function may not see it

如我所料。有没有办法做到这一点？谢谢！

Answer 1

您无法从 table 中查找行（对象），因为这会导致您看到并期望看到的变异 table 错误。

可以直接引用受影响的对象，at least from 10g:

You can use the OBJECT_VALUE pseudocolumn in a trigger on an object table since 10g Release 1 (10.1). OBJECT_VALUE means the object as a whole. This is one example of its use. You can also call a PL/SQL function with OBJECT_VALUE as the datatype of an IN formal parameter.

所以你可以这样做：

BEGIN

    DBMS_OUTPUT.PUT_LINE('Profit percentage: ' || :NEW.OBJECT_VALUE.getProfit());

END;
/

更新后在 DML 触发器中调用对象成员函数（ORACLE 数据库）

Call object member function in a DML trigger after update (ORACLE database)

database

oracle

triggers

object

mutating-table