Changing default transition properties
After constraint checking, you may want to change default transition properties to improve performance by making sure the constraint is evaluated only when you know this is necessary. For example only on UPDATE and not on INSERT or DELETE.
For each day of a scheduled tour, that is, each day between the start_date and return_date in table SCHEDTOUR, there is a record in table DAY containing program details about the tour day. If the SCHEDTOUR dates are changed, you want the DAY dates to change along with them. Your constraint SQL statement is:
The constraint checker produces the default transition properties:
Transition Table = SCHEDTOUR
Alias = ST
Fire On Insert = Always
Fire On Delete = Always
Fire On Update = UsedColumns
You know that in fact the constraint need not be evaluated on INSERT or DELETE. On INSERT, the outcome of the subquery is NULL so the constraint either has no effect or, if DAY_DATE is a mandatory column, will raise an error. On DELETE, presumably DAY records are deleted by cascading delete from SCHEDTOUR.
Change these 2 transition properties:
Fire On Insert = Never
Fire On Delete = Never