| Author: Sriram 05 Oct 2008 | Member Level: Gold Points : 2 |
Trigger;
Trigger is an Self Contained block of Statements ,Trigger has fired when an DML Statements(Insert,update,delete) statements,
Sql Server 2005 supporting on DDL Statements also.
There are two types of Trigger is available
1) instead of Trigger
2) After Trigger
1) Instead Trigger : First checking the Condition after its fired.
2) After Trigger : First Fired then after Checking the Condition.
Thanks
SriramRamaswamy
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| Author: Mari raj k 08 Oct 2008 | Member Level: Silver Points : 2 |
Types of Triggers
A trigger:
• Is a PL/SQL block or a PL/SQL procedure
associated with a table, view, schema, or the
database
• Executes implicitly whenever a particular event
takes place
• Can be either:
– Application trigger: Fires whenever an event occurs
with a particular application
– Database trigger: Fires whenever a data event (such
as DML) or system event (such as logon or
shutdown) occurs on a schema or database
Types of Triggers
Application triggers execute implicitly whenever a particular data manipulation language (DML) event occurs within an application. An example of an application that uses triggers extensively is one developed with Oracle Forms Developer.
Database triggers execute implicitly when a data event such as DML on a table (an INSERT, UPDATE,
or DELETE triggering statement), an INSTEAD OF trigger on a view, or data definition language (DDL) statements such as CREATE and ALTER are issued, no matter which user is connected or which application is used. Database triggers also execute implicitly when some user actions or database system actions occur, for example, when a user logs on, or the DBA shut downs the database.
Note: Database triggers can be defined on tables and on views. If a DML operation is issued on a view, the INSTEAD OF trigger defines what actions take place. If these actions include DML operations on tables, then any triggers on the base tables are fired.
Database triggers can be system triggers on a database or a schema. With a database, triggers fire for
each event for all users; with a schema, triggers fire for each event for that specific user.
Guidelines for Designing Triggers
• Design triggers to:
– Perform related actions
– Centralize global operations
• Do not design triggers:
– Where functionality is already built into the Oracle
server
– That duplicate other triggers
• Create stored procedures and invoke them in a
trigger, if the PL/SQL code is very lengthy.
• The excessive use of triggers can result in
complex interdependencies, which may be difficult
to maintain in large applications.
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| Author: Mari raj k 08 Oct 2008 | Member Level: Silver Points : 2 |
Types of Triggers
A trigger:
• Is a PL/SQL block or a PL/SQL procedure
associated with a table, view, schema, or the
database
• Executes implicitly whenever a particular event
takes place
• Can be either:
– Application trigger: Fires whenever an event occurs
with a particular application
– Database trigger: Fires whenever a data event (such
as DML) or system event (such as logon or
shutdown) occurs on a schema or database
Types of Triggers
Application triggers execute implicitly whenever a particular data manipulation language (DML) event occurs within an application. An example of an application that uses triggers extensively is one developed with Oracle Forms Developer.
Database triggers execute implicitly when a data event such as DML on a table (an INSERT, UPDATE,
or DELETE triggering statement), an INSTEAD OF trigger on a view, or data definition language (DDL) statements such as CREATE and ALTER are issued, no matter which user is connected or which application is used. Database triggers also execute implicitly when some user actions or database system actions occur, for example, when a user logs on, or the DBA shut downs the database.
Note: Database triggers can be defined on tables and on views. If a DML operation is issued on a view, the INSTEAD OF trigger defines what actions take place. If these actions include DML operations on tables, then any triggers on the base tables are fired.
Database triggers can be system triggers on a database or a schema. With a database, triggers fire for
each event for all users; with a schema, triggers fire for each event for that specific user.
Guidelines for Designing Triggers
• Design triggers to:
– Perform related actions
– Centralize global operations
• Do not design triggers:
– Where functionality is already built into the Oracle
server
– That duplicate other triggers
• Create stored procedures and invoke them in a
trigger, if the PL/SQL code is very lengthy.
• The excessive use of triggers can result in
complex interdependencies, which may be difficult
to maintain in large applications.
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