pgadmin4/docs/en_US/trigger_dialog.rst

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.. _trigger_dialog:
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***********************
`Trigger Dialog`:index:
***********************
Use the *Trigger* dialog to create a trigger or modify an existing trigger. A
trigger executes a specified function when certain events occur.
The *Trigger* dialog organizes the development of a trigger through the
following dialog tabs: *General*, *Definition*, *Events*, and *Code*. The *SQL*
tab displays the SQL code generated by dialog selections.
.. image:: images/trigger_general.png
:alt: Trigger dialog general tab
:align: center
Use the fields in the *General* tab to identify the trigger:
* Use the *Name* field to add a descriptive name for the trigger. This must be
distinct from the name of any other trigger for the same table. The name will
be displayed in the *pgAdmin* tree control. Note that if multiple triggers of
the same kind are defined for the same event, they will be fired in
alphabetical order by name.
* Store notes about the trigger in the *Comment* field.
Click the *Definition* tab to continue.
.. image:: images/trigger_definition.png
:alt: Trigger dialog definition tab
:align: center
Use the fields in the *Definition* tab to define the trigger:
* Move the *Row trigger?* switch to the *No* position to disassociate the
trigger from firing on each row in a table. The default is *Yes*.
* Move the *Constraint trigger?* switch to the *Yes* position to specify the
trigger is a constraint trigger.
* If enabled, move the *Deferrable?* switch to the *Yes* position to specify
the timing of the constraint trigger is deferrable and can be postponed until
the end of the statement. The default is *No*.
* If enabled, move the *Deferred?* switch to the *Yes* position to specify the
timing of the constraint trigger is deferred to the end of the statement
causing the triggering event. The default is *No*.
* Use the drop-down listbox next to *Trigger Function* to select a trigger
function or procedure.
* Use the *Arguments* field to provide an optional (comma-separated) list of
arguments to the function when the trigger is executed. The arguments are
literal string constants.
Click the *Events* tab to continue.
.. image:: images/trigger_events.png
:alt: Trigger dialog events tab
:align: center
Use the fields in the *Events* tab to specify how and when the trigger fires:
* Use the drop-down listbox next to the *Fires* fields to determine if the
trigger fires *BEFORE* or *AFTER* a specified event. The default is *BEFORE*.
* Select the type of event(s) that will invoke the trigger; to select an event
type, move the switch next to the event to the *YES* position. The supported
event types are *INSERT*, *UPDATE*, *DELETE*, and *TRUNCATE*.
* Use the *When* field to provide a boolean condition that will invoke the
trigger.
* If defining a column-specific trigger, use the *Columns* field to specify the
columns or columns that are the target of the trigger.
Click the *Code* tab to continue.
.. image:: images/trigger_code.png
:alt: Trigger dialog code tab
:align: center
Use the *Code* field to specify any additional code that will be invoked when
the trigger fires.
Click the *SQL* tab to continue.
Your entries in the *Trigger* dialog generate a SQL command (see an example
below). Use the *SQL* tab for review; revisit or switch tabs to make any changes
to the SQL command.
Example
*******
The following is an example of the sql command generated by user selections in
the *Trigger* dialog:
.. image:: images/trigger_sql.png
:alt: Trigger dialog sql tab
:align: center
The example demonstrates creating a trigger named *log_update* that calls a
procedure named *log_account_update* that logs any updates to the *distributors*
table.
* Click the *Info* button (i) to access online help.
* Click the *Save* button to save work.
* Click the *Cancel* button to exit without saving work.
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* Click the *Reset* button to restore configuration parameters.