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[Oracle]each row and table level triggers

kooyee — Sat, 05 Apr 2008 11:36:00 GMT

row level triggers : 是每个row改变�Ӟ��触发trigger�?比如�Q�２个row update�Q�触发２�ơ�?br />
table level triggers: 是table改变�Ӟ��触发trigger。无论几个row改变都没影响, 比如�Q?个row update触发1��?,�Q�个row update�Q�也触发1�ơ�?br />
��Z��转个教程

Before / for each row trigger

A before trigger is called before because it fires before the new values (:new.field_name) are stored in the table. That means that the new value can be changed in the trigger.

create table t_update_before_each_row (
txt varchar2(10)
);
create table log (
txt varchar2(20)
);
create trigger update_before_each_row
before update on t_update_before_each_row
for each row
begin
:new.txt := upper(:new.txt);
insert into log values ('old: ' || :old.txt);
insert into log values ('new: ' || :new.txt);
end update_before_each_row;
/

insert into t_update_before_each_row values('one');
insert into t_update_before_each_row values('two');
insert into t_update_before_each_row values('three');
insert into t_update_before_each_row values('four');

Updating (that is: concatenating the value with itself) the rows containing two and three:

update t_update_before_each_row set txt = txt || txt
where substr(txt,1,1) = 't';

select * from t_update_before_each_row;

As can be seen by the output of the select statement, the trigger changed the values of the new values; they're in uppercase now:

one
TWOTWO
THREETHREE
four

The log displays the old and new values:

select * from log;

old: two
new: TWOTWO
old: three
new: THREETHREE

Cleaning up:

drop table t_update_before_each_row;
drop table log;

After / for each row trigger

In contrast to a before trigger, an after trigger does not allow to change :new.field_name because the value is, when the trigger fires, already written to the table.

If one tries to assign a value to :new.field_name, Oracle throws an ORA-04084: cannot change NEW values for this trigger type.

create table t_update_after_each_row (
txt varchar2(10)
);
create table log (
txt varchar2(20)
);
create trigger update_after_each_row
after update on t_update_after_each_row
for each row
begin
-- :new.txt := upper(:old.txt); -- ORA-04084: cannot change NEW values for this trigger type
insert into log values ('old: ' || :old.txt);
insert into log values ('new: ' || :new.txt);
end update_after_each_row;
/

insert into t_update_after_each_row values('one');
insert into t_update_after_each_row values('two');
insert into t_update_after_each_row values('three');
insert into t_update_after_each_row values('four');

update t_update_after_each_row set txt = txt || txt
where substr(txt,1,1) = 't';

select * from t_update_after_each_row;

one
twotwo
threethree
four

select * from log;

As the log table shows, it is possible to use :new and :old although it's not possible to assign something to :new.

old: two
new: twotwo
old: three
new: threethree

Cleaning up:

drop table t_update_after_each_row;
drop table log;

Table level trigger

A table level trigger is a trigger that doesn't fire for each row to be changed. Accordingly, it lacks the for each row. Consequently, both, the :new and :old are not permitted in the trigger's PL/SQL block, otherwise, an ORA-04082: NEW or OLD references not allowed in table level triggers is thrown.

create table t_update_before (
txt varchar2(10)
);
create table log (
txt varchar2(20)
);
create trigger update_before
before update on t_update_before
begin
-- :new.txt := upper(:old.txt); -- ORA-04082
insert into log values ('update trigger');
end update_before;
/

insert into t_update_before values('one');
insert into t_update_before values('two');
insert into t_update_before values('three');
insert into t_update_before values('four');

update t_update_before set txt = txt || txt
where substr(txt,1,1) = 't';

select * from t_update_before;

one
twotwo
threethree
four

Although two rows were updated, only one record is found in the log table:

select * from log;

update trigger

An update statement that doesn't update any row:

update t_update_before set txt = txt || txt
where txt = 'no update';

Still, the trigger fires...

select * from log;

... which results in another row found in the log table:

update trigger
update trigger

Cleaning up:

drop table t_update_before;
drop table log;

Order of execution

Oracle allows to create multiple triggers on the same table. The order of the execution of these triggers is undeterministic (or random, if you want this word) except that all before triggers fire before the after triggers.

kooyee 2008-04-05 19:36 发表评论

[MYSQL] SQLException: No suitable driver

kooyee — Fri, 16 Nov 2007 12:33:00 GMT

问题可能�?建立database�q�接�Ӟ��url的格式不正确引�v的�?br />
正确格式�?

jdbc:mysql://localhost : 3306/database

kooyee 2007-11-16 20:33 发表评论

kooyee — Sat, 10 Nov 2007 13:00:00 GMT

http://dev.mysql.com/doc/refman/5.1/zh/index.html

5.8. MySQL用户账户��理

5.8.1. MySQL用户名和密码
5.8.2. 向MySQL增加新用戯�̎�?/a>
5.8.3. 从MySQL删除用户账户
5.8.4. 限制账户资源
5.8.5. 讄��账户密码
5.8.6. 使你的密码安�?/a>
5.8.7. 使用安全�q�接

5.8.2. 向MySQL增加新用戯�̎�?/h3>

可以用两�U�方式创�?span>MySQL账户�Q?/p>

· 使用GRANT语句

· 直接操作MySQL授权�?/p>

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创徏账户的其它方法是使用MySQL账户��理功能的第三方�E�序�?span>phpMyAdmin��x(ch��ng)��一个程序�?/p>

下面的示例说明如何��?strong>MySQL客户端程序来讄��新用戗��假定按�?a title="2.9.3. Securing the Initial MySQL Accounts" >2.9.3节，“使初始MySQL账户安全”描述�?默认值来讄��权限。这说明��Z��(ji��n)更改�Q�你必须�?span>MySQL root用户�q�接MySQL服务器，�q�且root账户必须�?span>mysql数据库的INSERT权限�?span>RELOAD��理权限�?/p>

首先�Q��?strong>MySQL�E�序�?span>MySQL root用户来连接服务器�Q?/p>

shell> MySQL --user=root MySQL

如果你�ؓ(f��)root账户指定�?ji��n)密码，�q�需要�ؓ(f��)�?strong>MySQL命��o(h��)和本节中的其它命令提�?span>--password�?span>-p选项�?/p>

�?span>root�q�接到服务器上后�Q�可以添加新账户。下面的语句使用GRANT来设�|�四个新账户�Q?/p>

mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'localhost'

    ->     IDENTIFIED BY 'some_pass' WITH GRANT OPTION;

mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'%'

    ->     IDENTIFIED BY 'some_pass' WITH GRANT OPTION;

mysql> GRANT RELOAD,PROCESS ON *.* TO 'admin'@'localhost';

mysql> GRANT USAGE ON *.* TO 'dummy'@'localhost';

�?span>GRANT语句创徏的�̎��h��下面的属性：(x��)

· 其中两个账户有相同的用户�?span>monty和密�?span>some_pass。两个�̎户均��U�用戯�̎��P��h��完全的权限可以做��M��事情。一个�̎�?span> ('monty'@'localhost')只用于从本机�q�接时。另一个�̎�?span>('monty'@'%')可用于从其它��L��q�接。请注意monty的两个�̎户必��能从�Q何主��Z��monty�q�接。没�?span>localhost账户�Q�当monty从本��接时�Q?strong>mysql_install_db创徏�?span>localhost的匿名用戯�̎户将占先。结果是�Q?span>monty��被视�ؓ(f��)匿名用户。原因是匿名用户账户�?span>Host列值比'monty'@'%'账户更具体，�q�样�?span>user表排序顺序中排在前面�?span>(user表排序的讨论参见5.7.5节，“讉K��控制, 阶段1�Q�连接核�?#8221;�Q?span>�?

· 一个�̎��h��用户�?span>admin�Q�没有密码。该账户只用于从本机�q�接。授予了(ji��n)RELOAD�?span>PROCESS��理权限。这些权限允�?span>admin用户执行mysqladmin reload�?strong>mysqladmin refresh�?strong>mysqladmin flush-xxx命��o(h��)�Q�以�?strong>mysqladmin processlist。未授予讉K��数据库的权限。你可以通过GRANT语句��d��此类权限�?/p>

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除了(ji��n)GRANT�Q�你可以直接�?span>INSERT语句创徏相同的�̎��P��然后使用FLUSH PRIVILEGES告诉服务器重载授权表�Q?/p>

shell> mysql --user=root mysql

mysql> INSERT INTO user

    ->     VALUES('localhost','monty',PASSWORD('some_pass'),

    ->     'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y');

mysql> INSERT INTO user

    ->     VALUES('%','monty',PASSWORD('some_pass'),

    ->     'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y');

mysql> INSERT INTO user SET Host='localhost',User='admin',

    ->     Reload_priv='Y', Process_priv='Y';

mysql> INSERT INTO user (Host,User,Password)

    ->     VALUES('localhost','dummy','');

mysql> FLUSH PRIVILEGES;

当你�?span>INSERT创徏账户时��?span>FLUSH PRIVILEGES的原因是告诉服务器重��L��权表。否则，只有重启服务器后更改方会(x��)被注意到。��?GRANT�Q�则不需要��?span>FLUSH PRIVILEGES�?/p>

�?span>INSERT使用PASSWORD()函数是�ؓ(f��)�?ji��n)加密密码�?span>GRANT语句��Z��加密密码�Q�因此不需�?span>PASSWORD()�?/p>

'Y'值启用�̎��h��限。对�?span>admin账户�Q�还可以使用更加可读�?span>INSERT扩充的语法（使用SET�Q��?/p>

在�ؓ(f��)dummy账户�?span>INSERT语句中，只有user表中�?span>Host�?span>User�?span>Password列记录�ؓ(f��)指定的倹{��没有一个权限列为显式设�|�，因此MySQL��它们均指定�?默认�?span>'N'。这��L(f��ng)��同于GRANT USAGE的操作�?/p>

��h��意要讄��用户账户�Q�只需要创��Z��个权限列讄��?span>'Y'�?span>user表条目�?span>user表权限�ؓ(f��)全局权限�Q�因此其�?授权表不再需要条目�?/p>

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要想�?span>GRANT创徏账户�Q��用下面的语句�Q?/p>

shell> MySQL --user=root MySQL

shell> mysql --user=root mysql

mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP

    ->     ON bankaccount.*

    ->     TO 'custom'@'localhost'

    ->     IDENTIFIED BY 'obscure';

mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP

    ->     ON expenses.*

    ->     TO 'custom'@'whitehouse.gov'

    ->     IDENTIFIED BY 'obscure';

mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP

    ->     ON customer.*

    ->     TO 'custom'@'server.domain'

    ->     IDENTIFIED BY 'obscure';

�q?span>3个�̎户可以用于：(x��)

· �W?span>1个�̎户可以访�?span>bankaccount数据库，但只能从本机讉K��?/p>

· �W?span>2个�̎户可以访�?span>expenses数据库，但只能从��L��whitehouse.gov讉K��?/p>

· �W?span>3个�̎户可以访�?span>customer数据库，但只能从��L��server.domain讉K��?/p>

要想不用GRANT讄��custom账户�Q��?span>INSERT语句直接修改授权表：(x��)

shell> mysql --user=root mysql

mysql> INSERT INTO user (Host,User,Password)

    ->     VALUES('localhost','custom',PASSWORD('obscure'));

mysql> INSERT INTO user (Host,User,Password)

    ->     VALUES('whitehouse.gov','custom',PASSWORD('obscure'));

mysql> INSERT INTO user (Host,User,Password)

    ->     VALUES('server.domain','custom',PASSWORD('obscure'));

mysql> INSERT INTO db

    ->     (Host,Db,User,Select_priv,Insert_priv,

    ->     Update_priv,Delete_priv,Create_priv,Drop_priv)

    ->     VALUES('localhost','bankaccount','custom',

    ->     'Y','Y','Y','Y','Y','Y');

mysql> INSERT INTO db

    ->     (Host,Db,User,Select_priv,Insert_priv,

    ->     Update_priv,Delete_priv,Create_priv,Drop_priv)

    ->     VALUES('whitehouse.gov','expenses','custom',

    ->     'Y','Y','Y','Y','Y','Y');

mysql> INSERT INTO db

    ->     (Host,Db,User,Select_priv,Insert_priv,

    ->     Update_priv,Delete_priv,Create_priv,Drop_priv)

    ->     VALUES('server.domain','customer','custom',

    ->     'Y','Y','Y','Y','Y','Y');

mysql> FLUSH PRIVILEGES;

�?span>3�?span>INSERT语句�?span>user表中加入条目�Q�允许用�?span>custom从各�U�主机用�l�定的密码进行连接，但不授予全局权限(所有权限设�|��ؓ(f��) 默认�?span>'N')。后�?span>3�?span>INSERT语句�?span>user表中加入条目�Q��ؓ(f��)custom授予bankaccount�?span>expenses�?span>customer数据库权限，但只能从合适的��L��讉K��?span>通常若直接修�?授权表，则应告诉服务器用FLUSH PRIVILEGES重蝲授权表，使权限更改生效�?/span>

如果你想要让某个用户从给定域的所有机器访�?span>(例如�Q?/span>mydomain.com)�Q�你可以在�̎户名的主机部分��用含‘%’通配�W�的GRANT语句�Q?/span>

mysql> GRANT ...

    ->     ON *.*

    ->     TO 'myname'@'%.mydomain.com'

    ->     IDENTIFIED BY 'mypass';

要想通过直接修改授权表来实现�Q?/p>

mysql> INSERT INTO user (Host,User,Password,...)

    ->     VALUES('%.mydomain.com','myname',PASSWORD('mypass'),...);

mysql> FLUSH PRIVILEGES;

kooyee 2007-11-10 21:00 发表评论

av大大超碰在线,暧暧视频在线免费观看,91成人在线播放

[Oracle]each row and table level triggers

Before / for each row trigger

After / for each row trigger

Table level trigger

Order of execution

[MYSQL] SQLException: No suitable driver

5.8. MySQL用户账户���理

5.8.2. 向MySQL增加新用戯�̎�?/h3>

5.8. MySQL用户账户��理