The optimizer uses system catalogs indicating how many rows there are and how well the indexes are formed to figure out what query path to use.
优化程序采用系统目录，说明那里有多少行，以及构造了较好的索引来计算所采用的查询路径。
This is because the path expression in the query targets only elements that have no namespaces.
这是因为该查询中的路径表达式仅指向没有名称空间的元素。
As you'll see shortly, DB2 can use both of these indexes to generate an efficient access path for our query.
正如您马上就会看到的，DB 2可以使用这两个索引来为我们的查询产生一个高效的访问路径。
These tools also have a basic XML path discovery capability, but it is associated with the XSLT editor, so it is not really useful for query development.
这些工具还具有基本的xml路径发现功能，但是它与XSLT编辑器相关，因此对于查询开发并不真的有用。
JEST applies a special interpretation to the path and query segments to translate them to an appropriate persistence operation.
JEST会对路径和查询部分进行特殊解析，将它们转换成一个正确的持久化操作。
This prevents attempts to disguise requests for dangerous file name extensions by putting a safe file name extension in the path information or query string portion of the URL.
的请求。这样可以防止通过将安全的文件扩展名放入url的路径信息或查询字符串部分，以达到伪装请求中的危险文件扩展名的企图。
If your queries execute without error but return no data, double-check the path expressions and namespace declarations in your query.
如果查询能够执行，但是没有返回数据，那么请仔细检查查询中的路径表达式和名称空间声明。
This means the optimizer will always attempt to formulate an access path for each query that reduces overall cost.
这意味着优化器将始终尝试为每个查询制定减少总体成本的存取路径。
Also, before selecting the access path, the optimizer first performs a series of query transformations to increase the number of access paths available.
还有，在选择访问路径之前，优化器首先会执行一系列查询转换以增加可用访问路径的数目。
That simple step could lead to a new access path that might dramatically improve query performance.
这个简单的步骤可能产生新的访问路径，可能显著改进查询性能。
Any query such as the one in Listing 1 has a precise path to the specified datum, which a DBMS can quickly determine in balanced trees and byte-offset codings.
如清单1中所示的任何查询都有到指定数据的精确路径，DBMS可以迅速地在均衡树和字节偏移编码中确定它。
Query XML data that contains namespaces requires you to specify appropriate namespace information in your path expressions.
当查询包含名称空间的XML数据时，需要在路径表达式中指定适当的名称空间信息。
The real distinction between path components and query parameters is that between hierarchical versus unordered arguments.
路径成分与查询参数之间真正的差异是，前者是层次化的，而后者是无次序的。
The access path of the query: How are the tables accessed?
查询的访问路径：如何访问这些表？
A new feature of the query optimizer supports a new type of index scan, called an index self-join path.
查询优化器的一项新特性支持一种新的索引扫描，即索引自连接路径。
XML-based query languages are constructed to reach any arbitrary position within an XML document's "graph" using sequences of edge labels and delimiters representing a path.
基于XML的查询语言被构造来，使用表示路径的边标签和定界符序列达到XML文档图中的任意位置。
When you've looked at the access path selected by DB2 for your target query, ask yourself this question: Should DB2 have selected a different access path for the query?
在查看DB2为目标查询选择的访问路径时，问自己一个问题：DB2应该为这个查询选择不同的访问路径吗？
In many cases, it is possible to write a query by using either a FLWOR expression or a path expression.
在很多情况下，可以任意使用FLWOR表达式或路径表达式编写查询。
If the SQL statement is badly coded, it is difficult for the optimizer to transform the query, leaving fewer options available for choosing an optimal access path.
如果sql语句设计得很糟，优化器就很难转换查询，在选择最佳访问路径时的选择就很少。
The SQL compiler USES query optimization to select the best performing access path for any given SQL statement (within a reasonable amount of time, of course).
SQL编译器使用查询优化来为任何给定的sql语句选择表现最好的访问路径(当然，这要在合理的时间内)。
Another way to provide a new and better access path for a query is through the use of DB2's materialized query table (MQT) functionality.
为查询提供更好的访问路径的另一种方法是使用DB2的物化查询表(MQT)功能。
An access path graph not only describes the "operational details" of query execution, it also describes how the data flows.
访问路径图不但描述“操作细节”，而且描述数据如何流动。
The description of each operation includes a Query Tuner access path graph that explains its operational semantics.
每一个操作的描述都包括一个解释其操作语义的QueryTuner访问路径图。
Table 1 describes the input, output, and function of several operation nodes that typically appear in an Optim Query Tuner access path graph.
表1描述通常出现在OptimQueryTuner访问路径图上的输入、输出和几个操作节点的功能。
An index scan is typically shown in Query Tuner as a group of four nodes in the access path graph.
在访问路径图中，一个索引扫描通常作为一组四个节点显示在QueryTuner上。
Intuitively, an access path is a procedural description of query execution that consists of three components.
直观地说，访问路径是查询执行的程序说明，其包括三个组件。
XPath (the XML Path language) is a powerful query language for selecting nodes in an XML document.
XPath (XMLPath语言)是一种强大的查询语言，用于选择XML文档中的节点。
The SQL statement in Listing 2 creates the access path graph shown on the right side of the Optim Query Tuner screenshot in Figure 2.
清单2中的sql语句创建如图2上的OptimQueryTuner截图右侧所示的访问路径图。
In that case, reorganizing the index might lead to its selection as part of a better-performing query access path.
在这种情况下，重新组织索引可能会影响DB2的选择，可能产生性能更好的查询访问路径。
The following sub section steps a user through obtaining the search path for the template to be used as a global IBM Query Studio template.
以下小节逐步指导用户获取将用作全局IBMQueryStudio模板的模板搜索路径。
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