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Oracle OCP 1Z0-050（37题）解析

QUESTION 37:

Which statements are true regarding the Query Result Cache? (Choose all that apply.)

A. It can store the results from normal as well as flashback queries.

B. It can be set at the system, session, or table level.

C. It is used only across statements in the same session.

D. It can store the results of queries based on normal, temporary, and dictionary tables.

Answer: A,B

参考Oracle官方文档：

SQL Query Result Cache

The database can store the results of queries and query fragments in the SQL query result cache, using the cached results for future queries and query fragments. Most applications benefit from this performance improvement.

For example, suppose an application runs the same SELECT statement repeatedly. If the results are cached, then the database returns them immediately. In this way, the database avoids the expensive operation of rereading blocks and recomputing results. The database automatically invalidates a cached result whenever a transaction modifies the data or metadata of database objects used to construct that cached result.

Users can annotate a query or query fragment with a RESULT_CACHE hint to indicate that the database should store results in the SQL query result cache. The RESULT_CACHE_MODE initialization parameter determines whether the SQL query result cache is used for all queries (when possible) or only for annotated queries.

关于Result Cache的更多特性随后补充示例。

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