Updating an oracle view dating guys in navy
There are two types of refresh modes and 4 types of refresh types.create materialized view m_dept build immediate refresh fast on commit enable query rewrite as select * from dept; build immediate - populate the materialized view right away refresh fast on commit - use the fast refresh method using the logs create above enable query rewrite - Oracle CBO will rewrite queries to use the new materialized view.If this happens, the UPDATE will terminate with an error ("subquery may return only one row"). Say you would like to take transformed data and use it to update our dimension table.Does it mean delete all employees that are in department LCR?
The information displayed by this view is meaningful only for inherently updatable views.This is where the CBO comes to play as it now has a choice to use the view to update the table of use the source tables, it calculates the total cost on each taking account for I/O, CPU and memory usage because the materialized has the data already summarized your queries should cost less in resources and hence should run more quicker.Sometimes the CBO needs a little help in using the materialized view, this is achieved using hints within the statement see SQL query optimization.Using Views A view is a virtual table consisting of a stored query, it contains no data.A view does not exist, basically its a definition defined within the data dictionary, lots of the DBA_ are views.
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Notes on Updatable Views An updatable view is one you can use to insert, update, or delete base table rows.