Re: Devx Database Comparison [Updated]

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От Greg Sabino Mullane
Тема Re: Devx Database Comparison [Updated]
Дата
Msg-id b2b264421c40fc730e0969e71b729b1f@biglumber.com
обсуждение исходный текст
Ответ на Re: Devx Database Comparison [Updated]  ("Joshua D. Drake" <jd@commandprompt.com>)
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Not sure exactly what the "Triggers: statement / row level" item means,
but mysql's trigger are definitely row only. Some funny stuff I found
while seeing if I had remembered that correctly below. From the official
mysql dev docs on triggers:

http://dev.mysql.com/tech-resources/articles/mysql-triggers.html

===

But remember that functions are subject to severe limitations: you cannot access tables
from within a function. So these statements are illegal inside a function:

   ALTER 'CACHE INDEX' CALL COMMIT CREATE DELETE
   DROP 'FLUSH PRIVILEGES' GRANT INSERT KILL
   LOCK OPTIMIZE REPAIR REPLACE REVOKE
   ROLLBACK SAVEPOINT 'SELECT FROM table'
   'SET system variable' 'SET TRANSACTION'
   SHOW 'START TRANSACTION' TRUNCATE UPDATE

Precisely the same limitation applies for triggers.

Triggers are very new. There are bugs. Therefore I give the same warning that I gave for
stored procedures. Do not try triggers with a database that has important data in it.
Instead, create a new database for testing purposes, and make sure this test database is
the default, whenever you are creating or using tables with triggers.

...

Lastly, the [older mysql] manual used to say that if you have triggers, then queries
will be slower. Forget that too, triggers have no effect on queries.

===

- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200511152239
http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8

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