Overview of Materialized Views (184)

Materialized views are schema objects that can be used to summarize, compute,
replicate, and distribute data. They are suitable in various computing environments
such as data warehousing, decision support, and distributed or mobile computing.

Materialized views are similar to indexes in several ways:
■ They consume storage space.
■ They must be refreshed when the data in their master tables changes.
■ They improve the performance of SQL execution when they are used for query
rewrites.
■ Their existence is transparent to SQL applications and users.
Unlike indexes, materialized views can be accessed directly using a SELECT statement.
Depending on the types of refresh that are required, they can also be accessed directly
in an INSERT, UPDATE, or DELETE statement.

A materialized view can be partitioned. You can define a materialized view on a
partitioned table and one or more indexes on the materialized view.

物化檢視
1. 物化檢視一種可以用於彙總 ,計算,複製,及釋出資料的方案物件.
她適用於資料倉儲,決策支援,分散式計算及移動計算等多種環境
2. 物化檢視與索引相似之處 : 佔用空間 ; 當主表資料變化後 , 需要重新整理 ; 使用查詢重寫可以改進SQL的執行效率
對於使用者和SQL應用來說是透明的 , 不同之處在於物化檢視可透過select語句執行訪問
3. 物化檢視可被分割槽 , 在分割槽上也可以定於物化檢視 , 在物化檢視上可建立索引

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