Programming trigger actions

Derby allows you to create triggers. When you create a trigger, you define an action or set of actions that are executed when a database event occurs on a specified table. A database event is a delete, insert, or update operation.

For example, if you define a trigger for a delete on a particular table, the trigger action is executed whenever someone deletes a row or rows from the table.

The "CREATE TRIGGER statement" topic in the Derby Reference Manual shows the complete CREATE TRIGGER syntax. This section provides information on defining the trigger action itself, which is only one aspect of creating triggers.

This section refers to the actions defined by the CREATE TRIGGER statement as the trigger actions.

• Trigger action overview
  A trigger action is a simple SQL statement.
• Performing referential actions
  Derby provides referential actions. Examples in this section are included to illustrate how to write triggers.
• Accessing before and after rows
  Many trigger actions need to access the values of the rows being changed.
• Examples of trigger actions
  This section provides some examples of triggers.
• Triggers and exceptions
  Exceptions raised by triggers have a statement severity; they roll back the statement that caused the trigger to fire.