What is the difference between Views and Materialized Views in Oracle

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Materialized views are disk based and are updated periodically based upon the query definition   Views are virtual only and run the query definition each time they are accessed

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Views  They evaluate the data in the tables underlying the view definition at the time the view is queried  It is a logical view of your tables  with no data stored anywhere else   The upside of a view is that it will always return the latest data to you  The downside of a view is that its performance depends on how good a select statement the view is based on  If the select statement used by the view joins many tables  or uses joins based on non-indexed columns  the view could perform poorly   Materialized views  They are similar to regular views  in that they are a logical view of your data  based on a select statement   however  the underlying query result set has been saved to a table  The upside of this is that when you query a materialized view  you are querying a table  which may also be indexed   In addition  because all the joins have been resolved at materialized view refresh time  you pay the price of the join once  or as often as you refresh your materialized view   rather than each time you select from the materialized view  In addition  with query rewrite enabled  Oracle can optimize a query that selects from the source of your materialized view in such a way that it instead reads from your materialized view  In situations where you create materialized views as forms of aggregate tables  or as copies of frequently executed queries  this can greatly speed up the response time of your end user application  The downside though is that the data you get back from the materialized view is only as up to date as the last time the materialized view has been refreshed     Materialized views can be set to refresh manually  on a set schedule  or based on the database detecting a change in data from one of the underlying tables  Materialized views can be incrementally updated by combining them with materialized view logs  which act as change data capture sources on the underlying tables   Materialized views are most often used in data warehousing   business intelligence applications where querying large fact tables with thousands of millions of rows would result in query response times that resulted in an unusable application     Materialized views also help to guarantee a consistent moment in time  similar to snapshot isolation

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Adding to Mike McAllister s pretty-thorough answer     Materialized views can only be set to refresh automatically through the database detecting changes when the view query is considered simple by the compiler   If it s considered too complex  it won t be able to set up what are essentially internal triggers to track changes in the source tables to only update the changed rows in the mview table   When you create a materialized view  you ll find that Oracle creates both the mview and as a table with the same name  which can make things confusing

User · Answer

Views  They evaluate the data in the tables underlying the view definition at the time the view is queried  It is a logical view of your tables  with no data stored anywhere else   The upside of a view is that it will always return the latest data to you  The downside of a view is that its performance depends on how good a select statement the view is based on  If the select statement used by the view joins many tables  or uses joins based on non-indexed columns  the view could perform poorly   Materialized views  They are similar to regular views  in that they are a logical view of your data  based on a select statement   however  the underlying query result set has been saved to a table  The upside of this is that when you query a materialized view  you are querying a table  which may also be indexed   In addition  because all the joins have been resolved at materialized view refresh time  you pay the price of the join once  or as often as you refresh your materialized view   rather than each time you select from the materialized view  In addition  with query rewrite enabled  Oracle can optimize a query that selects from the source of your materialized view in such a way that it instead reads from your materialized view  In situations where you create materialized views as forms of aggregate tables  or as copies of frequently executed queries  this can greatly speed up the response time of your end user application  The downside though is that the data you get back from the materialized view is only as up to date as the last time the materialized view has been refreshed     Materialized views can be set to refresh manually  on a set schedule  or based on the database detecting a change in data from one of the underlying tables  Materialized views can be incrementally updated by combining them with materialized view logs  which act as change data capture sources on the underlying tables   Materialized views are most often used in data warehousing   business intelligence applications where querying large fact tables with thousands of millions of rows would result in query response times that resulted in an unusable application     Materialized views also help to guarantee a consistent moment in time  similar to snapshot isolation

User · Answer

View  View is just a named query  It doesn t store anything  When there is a query on view  it runs the query of the view definition  Actual data comes from table    Materialised views  Stores data physically and get updated periodically  While querying MV  it gives data from MV

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Views  They evaluate the data in the tables underlying the view definition at the time the view is queried  It is a logical view of your tables  with no data stored anywhere else   The upside of a view is that it will always return the latest data to you  The downside of a view is that its performance depends on how good a select statement the view is based on  If the select statement used by the view joins many tables  or uses joins based on non-indexed columns  the view could perform poorly   Materialized views  They are similar to regular views  in that they are a logical view of your data  based on a select statement   however  the underlying query result set has been saved to a table  The upside of this is that when you query a materialized view  you are querying a table  which may also be indexed   In addition  because all the joins have been resolved at materialized view refresh time  you pay the price of the join once  or as often as you refresh your materialized view   rather than each time you select from the materialized view  In addition  with query rewrite enabled  Oracle can optimize a query that selects from the source of your materialized view in such a way that it instead reads from your materialized view  In situations where you create materialized views as forms of aggregate tables  or as copies of frequently executed queries  this can greatly speed up the response time of your end user application  The downside though is that the data you get back from the materialized view is only as up to date as the last time the materialized view has been refreshed     Materialized views can be set to refresh manually  on a set schedule  or based on the database detecting a change in data from one of the underlying tables  Materialized views can be incrementally updated by combining them with materialized view logs  which act as change data capture sources on the underlying tables   Materialized views are most often used in data warehousing   business intelligence applications where querying large fact tables with thousands of millions of rows would result in query response times that resulted in an unusable application     Materialized views also help to guarantee a consistent moment in time  similar to snapshot isolation

User · Answer

Materialized views are  the logical view of  data-driven by the select query but the result of the query will get stored in the table or disk  also the definition of the query will also store in the database   The performance of Materialized view it is better than normal View because the data of materialized view will be stored in table and table may be indexed so faster for joining also joining is done at the time of materialized views refresh time so no need to every time fire join statement as in case of view   Other difference includes in case of View we always get latest data but in case of Materialized view we need to refresh the view for getting latest data  In case of Materialized view we need an extra trigger or some automatic method so that we can keep MV refreshed  this is not required for views in the database

User · Answer

Views are essentially logical table-like structures populated on the fly by a given query   The results of a view query are not stored anywhere on disk and the view is recreated every time the query is executed   Materialized views are actual structures stored within the database and written to disk   They are updated based on the parameters defined when they are created

User · Answer

A view uses a query to pull data from the underlying tables   A materialized view is a table on disk that contains the result set of a query   Materialized views are primarily used to increase application performance when it isn t feasible or desirable to use a standard view with indexes applied to it  Materialized views can be updated on a regular basis either through triggers or by using the ON COMMIT REFRESH option  This does require a few extra permissions  but it s nothing complex  ON COMMIT REFRESH has been in place since at least Oracle 10

User · Answer

Adding to Mike McAllister s pretty-thorough answer     Materialized views can only be set to refresh automatically through the database detecting changes when the view query is considered simple by the compiler   If it s considered too complex  it won t be able to set up what are essentially internal triggers to track changes in the source tables to only update the changed rows in the mview table   When you create a materialized view  you ll find that Oracle creates both the mview and as a table with the same name  which can make things confusing

User · Answer

A view uses a query to pull data from the underlying tables   A materialized view is a table on disk that contains the result set of a query   Materialized views are primarily used to increase application performance when it isn t feasible or desirable to use a standard view with indexes applied to it  Materialized views can be updated on a regular basis either through triggers or by using the ON COMMIT REFRESH option  This does require a few extra permissions  but it s nothing complex  ON COMMIT REFRESH has been in place since at least Oracle 10

User · Answer

Views are essentially logical table-like structures populated on the fly by a given query   The results of a view query are not stored anywhere on disk and the view is recreated every time the query is executed   Materialized views are actual structures stored within the database and written to disk   They are updated based on the parameters defined when they are created

User · Answer

Materialized views are  the logical view of  data-driven by the select query but the result of the query will get stored in the table or disk  also the definition of the query will also store in the database   The performance of Materialized view it is better than normal View because the data of materialized view will be stored in table and table may be indexed so faster for joining also joining is done at the time of materialized views refresh time so no need to every time fire join statement as in case of view   Other difference includes in case of View we always get latest data but in case of Materialized view we need to refresh the view for getting latest data  In case of Materialized view we need an extra trigger or some automatic method so that we can keep MV refreshed  this is not required for views in the database

User · Answer

Materialised view - a table on a disk that contains the result set of a query   Non-materiased view - a query that pulls data from the underlying table

User · Answer

Views are essentially logical table-like structures populated on the fly by a given query   The results of a view query are not stored anywhere on disk and the view is recreated every time the query is executed   Materialized views are actual structures stored within the database and written to disk   They are updated based on the parameters defined when they are created

User · Answer

Views are essentially logical table-like structures populated on the fly by a given query   The results of a view query are not stored anywhere on disk and the view is recreated every time the query is executed   Materialized views are actual structures stored within the database and written to disk   They are updated based on the parameters defined when they are created

User · Answer

A view uses a query to pull data from the underlying tables   A materialized view is a table on disk that contains the result set of a query   Materialized views are primarily used to increase application performance when it isn t feasible or desirable to use a standard view with indexes applied to it  Materialized views can be updated on a regular basis either through triggers or by using the ON COMMIT REFRESH option  This does require a few extra permissions  but it s nothing complex  ON COMMIT REFRESH has been in place since at least Oracle 10

User · Answer

A view uses a query to pull data from the underlying tables   A materialized view is a table on disk that contains the result set of a query   Materialized views are primarily used to increase application performance when it isn t feasible or desirable to use a standard view with indexes applied to it  Materialized views can be updated on a regular basis either through triggers or by using the ON COMMIT REFRESH option  This does require a few extra permissions  but it s nothing complex  ON COMMIT REFRESH has been in place since at least Oracle 10

User · Answer

Materialised view - a table on a disk that contains the result set of a query   Non-materiased view - a query that pulls data from the underlying table

User · Answer

View  View is just a named query  It doesn t store anything  When there is a query on view  it runs the query of the view definition  Actual data comes from table    Materialised views  Stores data physically and get updated periodically  While querying MV  it gives data from MV

User · Answer

Adding to Mike McAllister s pretty-thorough answer     Materialized views can only be set to refresh automatically through the database detecting changes when the view query is considered simple by the compiler   If it s considered too complex  it won t be able to set up what are essentially internal triggers to track changes in the source tables to only update the changed rows in the mview table   When you create a materialized view  you ll find that Oracle creates both the mview and as a table with the same name  which can make things confusing

User · Answer

Views  They evaluate the data in the tables underlying the view definition at the time the view is queried  It is a logical view of your tables  with no data stored anywhere else   The upside of a view is that it will always return the latest data to you  The downside of a view is that its performance depends on how good a select statement the view is based on  If the select statement used by the view joins many tables  or uses joins based on non-indexed columns  the view could perform poorly   Materialized views  They are similar to regular views  in that they are a logical view of your data  based on a select statement   however  the underlying query result set has been saved to a table  The upside of this is that when you query a materialized view  you are querying a table  which may also be indexed   In addition  because all the joins have been resolved at materialized view refresh time  you pay the price of the join once  or as often as you refresh your materialized view   rather than each time you select from the materialized view  In addition  with query rewrite enabled  Oracle can optimize a query that selects from the source of your materialized view in such a way that it instead reads from your materialized view  In situations where you create materialized views as forms of aggregate tables  or as copies of frequently executed queries  this can greatly speed up the response time of your end user application  The downside though is that the data you get back from the materialized view is only as up to date as the last time the materialized view has been refreshed     Materialized views can be set to refresh manually  on a set schedule  or based on the database detecting a change in data from one of the underlying tables  Materialized views can be incrementally updated by combining them with materialized view logs  which act as change data capture sources on the underlying tables   Materialized views are most often used in data warehousing   business intelligence applications where querying large fact tables with thousands of millions of rows would result in query response times that resulted in an unusable application     Materialized views also help to guarantee a consistent moment in time  similar to snapshot isolation

User · Answer

Adding to Mike McAllister s pretty-thorough answer     Materialized views can only be set to refresh automatically through the database detecting changes when the view query is considered simple by the compiler   If it s considered too complex  it won t be able to set up what are essentially internal triggers to track changes in the source tables to only update the changed rows in the mview table   When you create a materialized view  you ll find that Oracle creates both the mview and as a table with the same name  which can make things confusing

[sql] What is the difference between Views and Materialized Views in Oracle?

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