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.

物化视图
1. 物化视图一种可以用于汇总 ,计算,复制,及发布数据的方案对象.
她适用于数据仓库,决策支持,分布式计算及移动计算等多种环境
2. 物化视图与索引相似之处 : 占用空间 ; 当主表数据变化后 , 需要刷新 ; 使用查询重写可以改进SQL的执行效率
对于用户和SQL应用来说是透明的 , 不同之处在于物化视图可通过select语句执行访问
3. 物化视图可被分区 , 在分区上也可以定于物化视图 , 在物化视图上可创建索引

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