Which of the following views is updatable?
The view name is represented by v. … SQL view is said to be updatable (that is, inserts, updates or deletes can be applied on the view) if which of the following conditions are satisfied by the query defining the view?
How do I check if a view is updatable?
You can check if a view in a database in updatable by querying the is_updatable column from the views table in the information_schema database.
Are Oracle views updatable?
Views in Oracle may be updateable under specific conditions. It can be tricky, and usually is not advisable. An updatable view is one you can use to insert, update, or delete base table rows. You can create a view to be inherently updatable, or you can create an INSTEAD OF trigger on any view to make it updatable.
Why views may not be updatable?
To be more specific, a view is not updatable if it contains any of the following: Aggregate functions ( SUM() , MIN() , MAX() , COUNT() , and so forth) … Reference to nonupdatable view in the FROM clause. Subquery in the WHERE clause that refers to a table in the FROM clause.
How many types of views are there?
There are total four types of views, based on the way in which the view is implemented and the methods that are permitted for accessing the view data. They are – Database Views, Projection Views, Maintenance Views, and Helps Views,.
What is the advantage of view in SQL?
Views can provide advantages over tables: Views can represent a subset of the data contained in a table. Consequently, a view can limit the degree of exposure of the underlying tables to the outer world: a given user may have permission to query the view, while denied access to the rest of the base table.
What makes a view updatable?
A view behaves like a table because you can query data from it. However, you cannot always manipulate data via views. A view is updatable if the statement against the view can be translated into the corresponding statement against the underlying table.
Are views updated automatically?
Yes, they are updated, every time you use them. I think Microsoft sums up what a View is quite clearly: A view can be thought of as either a virtual table or a stored query. Views are not automatically cached.
Can we modify view in SQL?
The ALTER VIEW command allows you to modify a view. A view is based on the result set from a query consisting of a SELECT statement or a UNION of two or more SELECT statements. … To determine if a specified view exists in the current namespace, use the $SYSTEM. SQL.
Can we insert and delete rows into a view?
Yes, possible to insert,update and delete to view. view is a virtual table. Same Perform as insert,update,delete query.. A view can be defined as a virtual table or a stored query and the data accessible through a view is not stored in the database as a distinct object.
Can you insert data into a view?
You can insert, update, and delete rows in a view, subject to the following limitations: If the view contains joins between multiple tables, you can only insert and update one table in the view, and you can’t delete rows. You can’t directly modify data in views based on union queries.
Which will create read only views?
A read-only view can be made updatable by means of triggers. A view will be read-only if its SELECT statement has any of the following characteristics: Specifies a row quantifier other than ALL (i.e., DISTINCT, FIRST, SKIP) Contains fields defined by subqueries or other expressions.