Data Warehousing Basics Question:
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Explain the difference between view and materialized view?


View - store the SQL statement in the database and let you use it as a table. Everytime you access the view, the SQL statement executes.

Materialized view - stores the results of the SQL in table form in the database. SQL statement only executes once and after that everytime you run the query, the stored result set is used. Pros include quick query results.

Views: At run time, the query will be executed against the database.

Materialized views: The data for the materialized view query will be generated at compile time.

Mviews can be created by the following ways:
1. Immediate - mview will be created along with data.
2. Deferred - Mview structure alone will be created. Data will be populated only when you refresh the mview.

We have the option of refreshing the mviews. It means when the data in the master table used in the mview query changes, the refreshing of mviews helps to get the updated (new) data for the mview.

Mview will behave very much like a table. At run time, data will be retrieved from the result set just as retrieved from a table. The retrieval time will be very fast unlike the views.

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