What is view merging in Oracle?
View merging merges the tables from the view into the outer query block, removing the view query block. After view merging, the query looks like this: Copy code snippet. Copied to Clipboard.
How can I see all views in Oracle?
ALL_VIEWS describes the views accessible to the current user. DBA_VIEWS describes all views in the database. USER_VIEWS describes the views owned by the current user.
What are different types of views in Oracle?
There are 2 types of Views in SQL: Simple View and Complex View. Simple views can only contain a single base table. Complex views can be constructed on more than one base table. In particular, complex views can contain: join conditions, a group by clause, a order by clause.
What is view MERGE?
View Compare/Merge (VCM) is the tool you use to compare two views or subsets of two views, referred to as the source and the target. As part of the process, you can merge item differences in the source view to the target view.
Is MERGE statement deterministic?
MERGE is what is known as a deterministic statement. That is, you can only update the same row of the target table once in the same MERGE statement.
How do I view views in Oracle SQL Developer?
To display views:
- In the Connections navigator in SQL Developer, navigate to the Views node for the schema that includes the view you want to display. If the view is in your own schema, navigate to the Views node in your schema.
- Open the Views node.
- Click the name of the view that you want to display.
What are different types of views?
There are three types of pictorial views:
What is a non-mergeable view?
Non mergeable views – Because a view is an encapsulation of a complex query, it is used as-if it were a discrete relational table. Hence, Oracle must pre-materialize a view whenever it is used in a query.
How do I merge two views in SQL Server?
The MERGEhint lets you merge a view on a per-query basis. If a view’s query contains a GROUPBYclause or DISTINCToperator in the SELECTlist, then the optimizer can merge the view’s query into the accessing statement only if complex view merging is enabled.
Can I merge a view query into the accessing statement?
If a view’s query contains a GROUPBYclause or DISTINCToperator in the SELECTlist, then the optimizer can merge the view’s query into the accessing statement only if complex view merging is enabled. Complex merging can also be used to merge an INsubquery into the accessing statement if the subquery is uncorrelated.
What is complex merging in SQL?
Complex merging can also be used to merge an INsubquery into the accessing statement if the subquery is uncorrelated. Complex merging is not cost-based–that is, the accessing query block must include the MERGEhint. Without this hint, the optimizer uses another approach. merge_hint::= Text description of merge_hint For example: