Oracle updating a view aaliyah dating ginuwine
To create a view use the create view command as seen in this example This command creates a new view called VIEW_EMP.
Note that this command does not result in anything being actually stored in the database at all except for a data dictionary entry that defines this view.
This means that every time you query this view, Oracle has to go out and execute the view and query the database data.
We can query the view like this: Oracle views offer some compelling benefits. Since a view is based on one common set of SQL, this means that when it is called it's less likely to require parsing.
Also, predicate pushing tends to break down as you stack more views on top of more views.
If you are going to start stacking views, carefully review the rules for predicate pushing in the Oracle documentation. Oracle views notes: This is an excerpt from the bestselling "Easy Oracle Jumpstart" by Robert Freeman and Steve Karam (Oracle ACE and Oracle Certified Master).
This is clearly a case of view abuse, and can lead to badly performing views.
Additional where clauses without a bind variable can still cause a hard parse! Views have long been used to hide the tables that actually contain the data you are querying.
Also, views can be used to restrict the columns that a given user has access to.
Using views for security on less complex databases is probably not a bad thing.
As databases become more complex, this solution becomes harder to scale and other solutions will be needed. Oracle supports pushing of predicates into a given view.
Predicate pushing has a number of restrictions that are beyond the scope of this book, but you can find them in the Oracle documentation.