An event target specifies the target for the trigger to be called. The target of a trigger event can be specified as a table or column name. If a column name is specified, the trigger is called only when the specified column is affected by the event. If a column is not specified, the trigger is called when any column of the table is affected. Only UPDATE and STATEMENT UPDATE events can specify a column as the event target.
The following example shows how to specify the score column of the history table as the event target of the example trigger.
CREATE TRIGGER example
...
BEFORE UPDATE ON history(score)
...