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