仅触发更改的值
Posted
技术标签:
【中文标题】仅触发更改的值【英文标题】:Trigger for only changed values 【发布时间】:2012-06-27 09:35:37 【问题描述】: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 |
---------------------------------------------
现在数据变了:
---------------------------------------------
| 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和更新的列(是的,我知道这没有任何意义,但他们使用的是 1970 年代的一些旧系统,他们想做一些日志记录等)。所以报表应该是这样的:
---------------------------------------------
| PK | Name | Address | Postal Code |
---------------------------------------------
| 2 | | | 44444 |
| 3 | | Dtreet7 | |
---------------------------------------------
这是我试过的:
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;
通过这个解决方案,我得到:
---------------------------------------------
| PK | Name | Address | Postal Code |
---------------------------------------------
| 2 | BB | Street2 | 44444 |
| 3 | CC | Dtreet7 | 33333 |
---------------------------------------------
我知道它在更新语句时插入子句中的某处,但我不知道如何根据我的要求更改此子句。有什么建议吗?
提前致谢。
【问题讨论】:
【参考方案1】:你需要这个:
在 UPDATE 触发器中,可以使用 UPDATING 指定列名 条件谓词来确定命名列是否正在 更新。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 documentation(9i)
11gR2 documentation
【讨论】:
+1,但是 9i 文档?仅触发更改的值。
作为一个例子(仅NOT NULL
支持)(带有 NULL 的比较运算符总是返回 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;
支持 NULL(感谢本文下方 cmets 中的@Oleg)(感谢@Chris Bandy 提供answer):
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;
【讨论】:
此解决方案不适用于 NULL 列。带 NULL 的比较运算符总是返回 FALSE。 @Oleg 感谢您提供非常有用的评论。更新了答案。【参考方案3】:对待 null :
... nvl(to_char(:new.department_id,' ') <> nvl(to_char(:old.department_id,' ') OR ...
【讨论】:
Oracle 认为空字符串 (''
) 为空值,因此 nvl(a_character_expression, '')
没有意义。
这是处理空值比较的最简单和最简洁的答案,尽管请参阅@MaximMandrik 的答案以了解触发器中所需的完整逻辑。以上是关于仅触发更改的值的主要内容,如果未能解决你的问题,请参考以下文章