What is key preserved table in Oracle?
What is key preserved table in Oracle?
A key-preserved table is a base table with a one-to-one row relationship with the rows in the view, via either the primary key or a unique key. In the example above, the cars table is a key-preserved table.
How do you resolve ORA 01779 Cannot modify a column which maps to a non key preserved table?
This ORA-01779 errors are related with the attempt was made to insert or update columns of a join view which map to a non-key-preserved table. You can Modify the underlying base tables directly and Try updating the tables directly. Or You can use work around is to use MERGE to do this.
What is updatable view?
An updatable view is a special case of a deletable view. A deletable view becomes an updatable view when at least one of its columns is updatable. A column of a view is updatable when all of the following rules are true: The view is deletable.
What is non updatable view in Oracle?
Non-Updateable Views may affect INSERT, UPDATE, and DELETE operations. One of the main reasons, why the views become non-updateable is because of inclusion of aggregate functions (which also includes DISTINCT), Group By, and Join.
Can we update data in materialized view Oracle?
Primary key materialized views that contain a selected class of subqueries can still be incrementally (or fast) refreshed, if each master referenced has a materialized view log. A fast refresh uses materialized view logs to update only the rows that have changed since the last refresh.
What is an updatable view in Oracle?
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.
How do I fix Ora 01779?
Action: Modify the underlying base tables directly. In your case, the ORA-01779 results because the update statement is malformed (by using an in-line view on two tables) and you want to issue the SQL update directly against one individual table, not the two tables that are specified in your DML syntax.
What is updatable view and non updatable view?
It means that the server always knows whether a view is updatable. If a view is not updatable, statements such UPDATE , DELETE , and INSERT are illegal and are rejected. (Even if a view is updatable, it might not be possible to insert into it, as described elsewhere in this section.)
What is the difference between view and materialized view?
Views are generally used when data is to be accessed infrequently and data in table get updated on frequent basis. On other hand Materialized Views are used when data is to be accessed frequently and data in table not get updated on frequent basis.
Can we do DML on materialized view?
A materialized view can be either read-only, updatable, or writeable. Users cannot perform data manipulation language (DML) statements on read-only materialized views, but they can perform DML on updatable and writeable materialized views.
How do you refresh data in materialized view?
A materialized view can be manually refreshed using the DBMS_MVIEW package. New features: Since Oracle 12c, statistics are calculated on the materialized view automatically due to online statistics gathering. dbms_mview.
