仅触发更改的值

Question

假设我们在表中有3条记录:orig_tab

---------------------------------------------
|  PK  |  Name  |  Address  |  Postal Code  |
---------------------------------------------
|   1  |  AA    |  Street1  |   11111       |
|   2  |  BB    |  Street2  |   22222       |
|   3  |  CC    |  Street3  |   33333       |
---------------------------------------------

现在数据发生了变化:

---------------------------------------------
|  PK  |  Name  |  Address  |  Postal Code  |
---------------------------------------------
|   1  |  AA    |  Street1  |   11111       |
|   2  |  BB    |  Street2  |   44444       |
|   3  |  CC    |  Dtreet7  |   33333       |
---------------------------------------------

客户想要的是更新记录,只有更新的列(是的,我知道它没有任何意义,但他们使用了一些20世纪70年代的旧系统,他们想要做一些记录等).所以报告表应该是这样的:

---------------------------------------------
|  PK  |  Name  |  Address  |  Postal Code  |
---------------------------------------------
|   2  |        |           |   44444       |
|   3  |        |  Dtreet7  |               |
---------------------------------------------

这就是我试过的:

CREATE OR REPLACE TRIGGER vr_reporting_trigger
   AFTER UPDATE ON orig_tab
   FOR EACH ROW
BEGIN
IF inserting THEN
INSERT INTO rep_tab(pk, name, address, code)
  SELECT :new.pk, :new.name, :new.address, :new,code FROM DUAL
  WHERE NOT EXISTS (SELECT 1 FROM rep_tab WHERE pk = :new.pk);
UPDATE rep_tab t SET t.name = :new.name, t.address = :new.address, t.code = :new.code 
   WHERE t.pk = :new.pk;
ELSIF updating THEN
IF :new.pk <> :old.pk THEN
     UPDATE rep_tab t
        SET t.name = :new.name, t.address = :new.address, t.code =: new.code
      WHERE t.pk = :old.pk ;
  END IF;
  MERGE INTO rep_tab d
  USING DUAL ON (d.pk = :old.pk)
  WHEN MATCHED THEN
  UPDATE SET d.name = :new.name, d.address = :new.address, d.code =: new.code
  WHEN NOT MATCHED THEN
  INSERT (d.pk,d.name, d.address, d.code) VALUES (:new.pk,:new.name, new.address, new.code);
END IF;
END;

有了这个解决方案,我得到:

---------------------------------------------
|  PK  |  Name  |  Address  |  Postal Code  |
---------------------------------------------
|   2  |  BB    |  Street2  |   44444       |
|   3  |  CC    |  Dtreet7  |   33333       |
---------------------------------------------

我知道在更新语句时插入claus中的某处,但我无法弄清楚如何根据我的要求更改此claus.有什么建议吗？

提前致谢.

Answer 1

你需要这个:

在UPDATE触发器中,可以使用UPDATING条件谓词指定列名,以确定是否正在更新命名列.例如,假设触发器定义如下:

CREATE OR REPLACE TRIGGER ...
... UPDATE OF Sal, Comm ON Emp_tab ...
BEGIN

... IF UPDATING ('SAL') THEN ... END IF;

END;

来自Oracle文档(9i)

11gR2文档

Answer 2

仅针对更改的值触发。

举个例子（仅NOT NULL支持）（带有 NULL 的比较运算符始终返回 FALSE）：

CREATE OR REPLACE TRIGGER trigger_department_update
  BEFORE UPDATE OF 
      department_id,
      cluster_id, 
      division_id, 
      macroregion_id, 
      address, 
      email
    ON cl_department
  FOR EACH ROW
BEGIN
  IF (
    :new.department_id != :old.department_id
    OR :new.cluster_id != :old.cluster_id
    OR :new.division_id != :old.division_id
    OR :new.macroregion_id != :old.macroregion_id
    OR :new.address != :old.address
    OR :new.email != :old.email
  ) 
    THEN :new.update_date := CURRENT_TIMESTAMP; 
  END IF;
END;

有了 NULL 支持（感谢本文下面评论中的@Oleg ）（感谢@Chris Bandy的回答）：

CREATE OR REPLACE TRIGGER trigger_department_update
  BEFORE UPDATE OF 
      department_id,
      cluster_id, 
      division_id, 
      macroregion_id, 
      address, 
      email
    ON cl_department
  FOR EACH ROW
BEGIN
  IF (
    ((:new.department_id <> :old.department_id OR :new.department_id IS NULL OR :old.department_id IS NULL) AND NOT (:new.department_id IS NULL AND :old.department_id IS NULL))
    OR ((:new.cluster_id <> :old.cluster_id OR :new.cluster_id IS NULL OR :old.cluster_id IS NULL) AND NOT (:new.cluster_id IS NULL AND :old.cluster_id IS NULL))
    OR ((:new.division_id <> :old.division_id OR :new.division_id IS NULL OR :old.division_id IS NULL) AND NOT (:new.division_id IS NULL AND :old.division_id IS NULL))
    OR ((:new.macroregion_id <> :old.macroregion_id OR :new.macroregion_id IS NULL OR :old.macroregion_id IS NULL) AND NOT (:new.macroregion_id IS NULL AND :old.macroregion_id IS NULL))
    OR ((:new.address <> :old.address OR :new.address IS NULL OR :old.address IS NULL) AND NOT (:new.address IS NULL AND :old.address IS NULL))
    OR ((:new.email <> :old.email OR :new.email IS NULL OR :old.email IS NULL) AND NOT (:new.email IS NULL AND :old.email IS NULL))
  ) 
    THEN :new.update_date := CURRENT_TIMESTAMP; 
  END IF;
END;