When a view is created using with check option, all views derived from the “base” view must satisfy its check option. Each row inserted through the derived view must be visible through the base view. Each row updated through the derived view must remain visible through the base view.
Consider the view stores_cal30, which is derived from stores_cal. The new view includes information about stores in California with payment terms of “Net 30”:
create view stores_cal30 as select * from stores_ca where payterms = "Net 30"
Because stores_cal was created using with check option, all rows inserted or updated through stores_cal30 must be visible through stores_cal. Any row with a state value other than “CA” is rejected.
stores_cal30 does not have a with check option clause of its own. This means that you can insert or update a row with a payterms value other than “Net 30” through stores_cal30. The following update statement would be successful, even though the row would no longer be visible through stores_cal30:
update stores_cal30 set payterms = "Net 60" where stor_id = "7067"
| Copyright © 2005. Sybase Inc. All rights reserved. |
|
|
