Triggers Wizard (DB2 LUW)
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A trigger defines a set of actions that take place in conjunction with, or are triggered, for a particular base table, with an insert, update, or delete statement. Triggers are dandy ways to validate input data, read from other tables for cross-referencing purposes, and other similar purposes. The Trigger Wizard lets you create a trigger without requiring you to know any of the underlying commands.
To create a new trigger using a wizard:
- Open a creation wizard for a trigger. For details, see Opening an Object Wizard.
- Use the following topics as a guide to setting properties and performing tasks as you pass through the wizard panels:
- Properties panel - for details, see Triggers (DB2 LUW) - Properties.
- Column Selection panel - for details, see Triggers (DB2 LUW) - Column Selection.
- Definition panel - for details, see Triggers (DB2 LUW) - Definition.
- Finally, use the Execute button to create the object.
Triggers (DB2 LUW) - Properties
When creating or editing a trigger, this tab/panel lets you work with the following settings:
| Setting | Description |
|---|---|
|
Table Schema and Table Name |
Choose the owner and name of the table for which the trigger is being created. |
|
Schema and Name |
Choose the owner and name of the trigger being created. |
|
Trigger Timing |
BEFORE: These triggers serve as extensions to the constraint subsystem and are most often used to validate input data, generate values for newly inserted rows, and read from other tables for cross-reference purposes. Note: Before triggers must be created as a For Each Row. AFTER: Such a trigger is run after the integrity constraint validations; they can be used to modify operations in the database or be used for activities beyond the database, like supporting an alert notification. |
|
Trigger Events |
An INSERT trigger must be associated with an INSERT statement. For example, if a data load operation doesn’t include an INSERT statement, the trigger will not be invoked. An UPDATE trigger can be associated with specific columns of the base table and will only be activated if those columns are updated. |
|
Trigger Type |
STATEMENT: (only fires once). ROW (fires for each affected row): The trigger runs as many times as there are rows in the affected section. If the set of affected rows is empty, the trigger doesn’t run. |
|
Old Table Alias |
Type the name of a temporary table of rows as they exist before they’re updated or deleted. |
|
New Table Alias |
Type a name for a temporary table of rows as they exist after they’re inserted or updated. |
|
Old Row Alias |
Type a name for the rows as they are before they’ve been deleted or updated. |
|
New Row Alias |
Type a name for the rows as they are after they’ve been inserted or updated. |
Triggers (DB2 LUW) - Column Selection
If you chose UPDATE as the Trigger Event, select the columns, select the check box beside each column that is to fire the trigger.
Triggers (DB2 LUW) - Definition
Complete the CREATE TRIGGER outline provided by typing or pasting the body of the trigger.