Oracle Report Trigger

There are five global triggers called the Report Triggers :-
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1. Before Parameter Form.
2. After Parameter Form.
3. Before Report
4. Between Pages
5. After Report

1. Before Parameter Form 
Fires before the Run time Parameter Form are displayed. Can 
access the PL/SQL global variables, report level columns 
and manipulate accordingly.

2. After Parameter Form 
Fires after the Run time Parameter form are displayed. Used 
to validate the parameter values.

3. Before Report 
Fires before the report is executed but after the queries
is parsed and date is fetched.

4. Between Pages 
Fires before each page of the report are formatted, except
the very first page. This page is used to customize page
formatting.

5. After Report 
Fires after the report previewer are exited, or after
report output is sent to a specified destination.

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Explain in details

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Before Form: Fires before the run-time Parameter Form is displayed. From this trigger, you can access and change the values of parameters, PL/SQL global variables, and report-level columns.

After Form: Fires after the run-time Parameter Form is displayed. From this trigger, you can access parameters and check their values. This trigger can also be used to change parameter values or, if an error occurs, return to the run-time Parameter Form. Columns from the data model are not accessible from this trigger.

Before Report: Fires before the report is executed but after queries are parsed and data is fetched.

Between Pages: Fires before each page of the report is formatted, except the very first page. This trigger can be used for customized page formatting.

After Report: Fires after you exit the Previewer, or after report output is sent to a specified destination, such as a file, a printer. This trigger can be used to clean up any initial processing that was done, such as deleting tables.