问题描述
我需要编写一些验证数据的代码。我有一个校验和，
我需要以相当复杂的方式计算，所以一个简单的
CHECK是不够的。哪个是DB2中最好的方法呢？
Ewa。
I need to write some code that will validate data. I have a checksum,
that I need to calculate in a rather complicated way, so a simple
CHECK is not enough. Which is the best way to do that in DB2?
Ewa.
推荐答案
如果验证涉及其他表，则IMO a触发前是您的最佳选择
：
CREATE TRIGGER ...
插入之前没有级联......
参考新的N
FOR EACH ROW
模式DB2SQL
WHEN（< condition）SIGNAL SQLSTATE ....
和一个类似的更新涉及的列。
如果相当复杂意味着复杂但只涉及这个表，我
仍将瞄准检查约束
我的2 skr
/ Lennart
If the validation involves other tables, IMO a before trigger is your
best option:
CREATE TRIGGER ...
NO CASCADE BEFORE INSERT ON ...
REFERENCING NEW AS N
FOR EACH ROW
MODE DB2SQL
WHEN ( <condition) SIGNAL SQLSTATE ....
and a similar one for update of involved columns.
If rather complicated means complicated but concern only this table, I
would still aim for check constraint
My 2 skr
/Lennart
是的，我忘了提到它确实只涉及一张桌子。我只是在我把它放在表格之前需要检查数据。你能否给我一些关于如何制定检查约束的提示（或链接到man），
包含循环和对数据的一些操作？我从来没写过
支票比CONSTRAINT更复杂一年检查（年（生日）> =
1986）
Ewa
Yes, I forgot to mention that it does concern only one table. I just
need to check the data before I put it in the table. Could you give me
some hints (or link to man) on how to make a check constraint, that
consists of loops and some operations on the data? I never wrote
checks more complicated than CONSTRAINT year CHECK (YEAR(birthday) >=
1986)
Ewa
是的，我忘了提到它确实只涉及一个表。我只是在我把它放在表格之前需要检查数据。你能否给我一些关于如何制定检查约束的提示（或链接到man），
包含循环和对数据的一些操作？我从来没写过
支票比CONSTRAINT更复杂一年CHECK（YEAR（生日）> =
1986）
Yes, I forgot to mention that it does concern only one table. I just
need to check the data before I put it in the table. Could you give me
some hints (or link to man) on how to make a check constraint, that
consists of loops and some operations on the data? I never wrote
checks more complicated than CONSTRAINT year CHECK (YEAR(birthday) >=
1986)
你必须写一个函数。
如果你说C UDF（最终没有被禁止）那么复杂，那就是你要走的路。
如果它只是几个IF和一个循环，只需要做一个SQL UDF。
我的拇指规则是SQL UDF不应该长于一个页面。
（25行）
干杯
Serge
-
Serge Rielau
DB2解决方案开发
IBM多伦多实验室
You have to write a function.
If it''s as complex as you say an C UDF (eventually unfenced) woudl be
the way to go.
If it''s just a couple of IFs and a loop, just do a SQL UDF.
My thumb rule is that SQL UDFs shouldn''t be longer than a page.
(25 lines)
Cheers
Serge
--
Serge Rielau
DB2 Solutions Development
IBM Toronto Lab
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