如果编目中没有列数据值分布信息，DB 2就会假设值是均匀分布的，这可能导致优化器选择非最优的访问路径。
Without column data-value distribution information in the catalog, DB2 will assume an even distribution of values, which may lead the optimizer to a sub-optimal access path.
尽管DB 2优化器对选择最佳访问路径有所帮助，但结果还是依赖于输入数据，优化器无法访问或控制这些数据。
Although the DB2 optimizer is helpful for selecting the best access path, the result depends on the input data, which is often not accessed or controlled by the optimizer.
访问计划描述访问路径，这些路径是DB 2优化器为sql语句访问数据而选择的。
Access plan describes the access path that the DB2 optimizer has chosen for accessing data for an SQL statement.
针对单个问题的优化：本质上，层次数据库就通过一条指定的路径来优化数据访问。
Optimized for one problem: By their nature, hierarchical databases optimized access to the data through one specific path.
不一致的统计数据还会误导优化器选择糟糕的访问路径。
The inconsistent statistics may also mislead the optimizer into choosing a bad access path.
优化器使用该数据模型来估计可以用于解决某个特定查询的其它存取路径的成本。
This data model is used by the optimizer to estimate the costs of alternative access paths that can be used to resolve a particular query.
优化器使用表大小、索引可用性以及数据分布等信息来确定响应该查询的最佳路径。
The optimizer USES information such as table sizes, availability of indexes, and data distribution to figure out the optimal way to answer the query.
如本文开头所提到的，统计数据是优化器作出关于访问路径的决策的基础。
As was mentioned at the beginning of this article, database statistics are the facts on which the optimizer makes decisions about access plans.
丢失的统计数据会让优化器高估或低估谓词的选择性，最终会选择低效的访问路径。
Missing statistics can cause the optimizer to overestimate or to underestimate the selectivity of a predicate, and eventually to select an inefficient access path.
请记住，优化器使用编目数据决定访问路径。
Keep in mind that this catalog data is what the optimizer USES to make access path decisions.
查询优化集中于cpu密集型(CPUbound)执行路径，而全缓存数据库将仍然集中于优化取页到大容量存储器的操作，而这已不再是问题。
Query optimization focuses on CPUbound execution paths, while a fully cached database will still be preoccupied with optimizing page fetches to mass storage that are no longer an issue.
不管哪种模式(3nf或Star)，Teradata查询优化器依赖于统计信息帮助确定最佳数据访问路径。
Regardless of schema (3nf or Star), the Teradata query optimizer relies on statistics to help it determine the best way to access data.
WebSphereFederationServer使用它的基于成本的优化器，确定检索和处理数据的最佳路径。
WebSphere Federation Server USES its cost based optimizer in order to determine the optimal access path to retrieve and process the data.
Soft RI结合统计数据使得优化器能够生成更有效的访问路径。
Soft RI in conjunction with statistics may enable the optimizer to generate a more efficient access path.
本文主要对XML数据库的查询语言、XML数据路径表达式查询的优化技术和XML数据的查询处理技术进行了重点研究。
This paper focuses on the query language of XML data, the technologies of path expression optimizing and the query processing of XML data.
给出了新的蓝牙基带的数据处理路径结构，采用串行方式实现可优化硬件资源。
The new data process path in Baseband is constructed to optimize hardware resource when it is realized by the means of serial bit processing.
提供了一种有大量的客户数据，只需对部分客户进行带有时间窗要求的货物配送的优化路径选择算法。
A kind of algorithm is provided to choose the optimized route for freight delivery that involves a great deal of clients' data, but, only deals with a part of them with the request of time Windows.
完成超越函数实现的数据路径设计，主要包括加法器、移位器、常数rom和旋转控制逻辑，同时针对“龙腾”C2微处理器的性能要求对各个部件进行优化设计。
Finish the design of data path, including adder, shifter, ROM and the control logic of the rotation, and optimize these parts in terms of the requirement of Longtium C2 microprocessor.
本文对数据库的查询技术进行分析，给出两种优化方法：分解查询和选择最优存取路径。
In this paper, first the query technology on database is analysed, then two optimization methods are offered: the disintegration query and the best access path selection.
我们研究这样一类权重网络的优化生长模式，在其上每两个节点之间的数据包的传送沿着优化路径进行。
We study an optimal growing mode for a class of weighted transportation networks on which data packets are exchanged between every pair of vertices along the optimal paths (OPs) connecting them.
路径表达式是XML数据查询语言的核心部分，但是目前针对路径表达式本身进行优化的研究却相对较少。
Path expression is one of the core components of most XML query languages. However, there are few researches on the issue of path expression optimization.
虚拟位置概念的引入减少了冗余的路由信息并优化了路由的路径，从而减轻了节点的负担并提升了数据传送的效率。
The idea of using virtual position lead to the benefit that less redundant routing information was generated, and thus the routing paths were optimized.
虚拟位置概念的引入减少了冗余的路由信息并优化了路由的路径，从而减轻了节点的负担并提升了数据传送的效率。
The idea of using virtual position lead to the benefit that less redundant routing information was generated, and thus the routing paths were optimized.
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