As a general rule, any processing that will affect the data retrieved by the report should
be performed in the Before Parameter Form and After Parameter Form trigger.(These are the two report trigger that fire before anything is parsed or fetched). There are five global report triggers. You cannot create new global report triggers. The trigger names indicate at point trigger fires:
1. Before Report: Fires before the report is executed but after queries are parsed.
2. After Report: Fires after you exit the Previewer, or after report output is sent to a specified destination, such as a file, a printer, or an Oracle Office userid. This trigger
can be used to clean up any initial processing that was done, such as deleting tables. Note,
however, that this trigger always fires, whether or not your report completed successfully.
3. 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. In the Previewer, this trigger only fires the first time that you go to page. If you subsequently return to the page, the trigger does not fire again.
4. Before Parameter Form: Fires before the Runtime Parameter Form is displayed. From this trigger, you can access and change the values of parameters, PL/SQL global variables, and report-level columns. If the Runtime Parameter Form is suppressed, this trigger still fires. Consequently, you can use this trigger for validation of command line parameters.
5. After Parameter Form: Fires after the Runtime 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 Runtime Parameter Form. Columns from the data model are not accessible from this trigger. If the Runtime Parameter Form is suppressed, the After Parameter Form trigger still fires. Consequently, you can use this trigger for validation of command line parameters or other data.
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