A recurring event is one which executes repeatedly, once at
start-time and once every
interval thereafter. A one-time event is one which will execute only once, at
The scheduler stores event definitions in an Events table where they can be seen with the
SHOW EVENTS command; each
CREATE EVENT inserts a new record into this table. Normal system behaviour is that once a one-time event has passed, or a recurring event's
end-time has passed, the event will be deleted from the table. There may be occasions, however, when one wishes to retain a record of past events, for example for review, or so that a particularly complex event can be rerun with
ALTER EVENT instead of retyping the entire event definition. The checkbox belongs to the label On completion preserve. This controls whether the event definition is deleted from the events table once it has completed, or kept. The default behaviour is to delete; checking this box causes the event to be preserved.