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What Is Trigger?

 
JiaPei Jen
Ranch Hand
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Where can I find the information about what trigger is?
 
H Johan Lekberg
Greenhorn
Posts: 4
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Hi,
This is from http://www.mysql.com/documentation/maxdb/a7/41ee1d605911d3a98800a0c9449261/content.htm
Is it what you wanted to know?
Trigger
While database procedures are called explicitly from the programming language of the application, triggers are special procedures that run implicitly on a base table (or a view table based on this base table) after a data manipulation statement has been executed.
The conditions under which a trigger is to be executed can be restricted further.
The trigger is executed for each row to which the SQL statement refers. The trigger can access both the old values (values before update or deletion) and the new values (values after update or insertion) in this row.
A trigger can call further triggers implicitly.
Triggers can be used to check complicated integrity rules, to initiate derived database modifications for the row in question, or to implement complex access protection rules.
The database system provides a language (special SQL syntax) that can be used to define database procedures and triggers.
http://www.mysql.com/documentation/maxdb/a7/41ee1d605911d3a98800a0c9449261/content.htm
 
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