Types of Triggers in Oracle Forms

There are mainly five types of form triggers.

1. On-Event:- These triggers are used to replace the default processing normally done by Oracle. Note that creating an On-Event trigger will completely replace the normal processing for this event. These are typically used when using Oracle Forms to create forms for Non-Oracle databases.                                                                                                                                         
2. When-Event:- These triggers are used to augment the normal processing done by Oracle. They fire in conjunction with the event that triggers them. For example, the When-Validate-Item trigger fires immediately after Form Builder validates data in an item. To augment the default validation checks that Form Builder performs you add code for the additional validation in a When-Validate-Item trigger.                                                                                                              
3. Post-Event:- These triggers are used to validate objects or data or perform auditing tasks just after an event occurs. They fire just following the occurrence of either a When-event or an On-event.                                                                                                                                                      
4. Pre-Event:- These triggers are used to prepare objects or data for the upcoming event. They fire just prior to the occurrence of either a When-event or an On-event. For example to ensure that a primary key is set to the value based on a sequence you would use a PRE-INSERT trigger.                                                                                                                                               
5. Key Triggers:- These triggers fires when the operator presses a specific key or key-sequence and replace the default action for the key. Remember that most GUI applications offer operators more than one way to execute commands. For instance, an operator might be able to execute a query by clicking a button, selecting a menu command, or pressing the "Execute Query" key. In such situations, it may be a mistake to place all of your application logic in a key trigger that may never fire. Similarly, in any mouse-driven application, you cannot rely entirely on key triggers for navigational keys like "Next Item" and "Next Block". Because operators can navigate with a mouse, they may choose not to use these keys for navigation, and the associated triggers would not be fired.