响应联合查询所必需的数据驻留在何处？
Where does the data reside that is necessary to respond to the federated query?
例如，考虑一个跨三个数据源的联邦联合查询。
For example, consider a federated union query across three sources.
只能将选择、交叉表和联合查询保存为这种格式。
You can only save select, crosstab , and union queries to this format.
根据映射定义，联合服务器将联合查询拆分为多个子操作。
According to the mapping definition, the federation server breaks down the federated query into multiple sub operations. Multiple factors influence this step.
例如，可以使用SQL编写联合查询，并可以指定对产品信息的访问。
For example, a federated query might be written in SQL and might specify access to product information.
源服务器可能在必须返回联合查询中请求的数据时受到工作负载增加的负面影响。
Source servers may be negatively impacted by increased workload when they have to return data that is requested in a federated query.
在soa上下文中应用数据联合模式时，需要在SOA内将一组联合查询作为服务启用并注册。
When applying the data federation pattern in an SOA context, a set of federated queries need to be enabled and registered as services within SOA.
该方案实现了异构数据库的透明访问和联合查询，为企业信息系统集成提供了一种技术方法。
It achieves transparent access and unified query, and provided one technical method for the enterprise information system integration.
联合查询的复杂性：为了执行查询，联合服务器需要执行多少筛选、联接、排序之类的子操作。
Complexity of the federated query: how many sub-operations such as filtering, joining, sorting, and so on, does the federation server need to execute to perform the query.
这意味着您能够获得典型的SQL联合查询的所有好处，但又不需要在数据库层预定义它们的关系。
This means you can get all the benefits of typical SQL join queries without the burden of predefining their relationships in the database layer.
每一个查询都包含相同数量的项目，它们具有相同的名称和顺序，这样它们就能够在第三个查询中实现联合。
Each query will contain the same number of items with the same names and in the same order so that they can be unioned in the third query.
跨异构数据源的高级数据和查询联合。
Advanced data and query federation across heterogeneous data sources.
正如上文所示，对具体类的查询只选择需要的数据，没有不必要的表连接和联合。
As shown above, queries on concrete classes only select the required data without unnecessary table joins or unions.
因此，大部分数据联合模式的实现对复杂转换功能的关注相对较少，而更强调查询优化技术。
Therefore, most implementations of the data federation pattern focus less on complex transformation capabilities and more on query optimization technologies.
联合服务器还必须提供查询优化功能，以最高效地响应请求。
The federation server must also provide query optimization capabilities in order to respond to the request most efficiently.
数据联合服务器负责接收定向到各种源的集成视图的查询。
The data federation server is responsible for receiving a query directed at an integrated view of diverse sources.
在一个查询中连接、联合、聚集来自多个数据源的数据并使它们相关的能力。
Ability to join, union, aggregate, and otherwise correlate data from multiple sources in a single query.
(记住您不能够联合这些查询，但是我仍然可以使用数字进行搜索。)
(Remember that you cannot do joins with these queries, but I can still search with Numbers.)
联合表或执行复杂查询都不需要任何复杂方案。
There is no complex scheme required to join tables or execute complex queries.
联合服务器将请求转换为对应的SQL查询或视图定义，以支持服务。
The federation server transforms the request into the corresponding SQL queries, or view definitions, to support the service.
通过利用高级查询处理功能，联合服务器可以在联合服务器本身和各个源之间最优地分布工作负载。
By leveraging advanced query processing capabilities, the federation server can optimally distribute the workload among the federation server itself and the various sources.
数据联合模式的有些实现可以将部分或全部子操作(子查询)以并行方式发送到集成源系统。
Some implementations of the data federation pattern are capable of sending some or all of the sub-operations (sub-queries) in parallel to the integrated source systems.
数据联合服务器——即实现数据联合模式的组件——必须针对传统非 SOA上下文提供标准查询接口。
The data federation server -- that is, the component that implements the data federation pattern -- must provide standard query interfaces for the non-traditional SOA context.
这就允许数据联合服务器接收对集成视图的查询和计算要执行的最优子操作数量和类型。
This allows the data federation server to receive queries against the integrated view and to calculate the optimum number and types of sub operations to perform.
要改进性能，联合需要经常使用缓存、物理查询表(MQT)以及分布式查询优化和执行。
To improve performance, federation frequently USES caching, materialized query tables (MQTs), and distributed query optimization and execution.
同时还支持各种高级功能，如跨多个XML查询的联合，使用xml类型的视图和模式验证。
Advanced features, such as joins across several XML queries, views with XML types, and schema validation are supported.
即使SimpleDB不允许查询中进行域联合，您也仍然可以在域中使用关联项。
Even though SimpleDB doesn't permit domain joins in queries, you can still have related items across domains.
例如，IBMInfoSphere InformationServer允许联合异构数据源以支持复杂的信息查询以及数据清理。
For example, IBM InfoSphere information Server enables federating heterogeneous data sources to support complex queries for information, as well as cleansing data.
设计健全的查询模式。不要害怕表联合，通常它们比非范式化更快。
Design sane query schemas. don't be afraid of table joins, often they are faster than denormalization.
“子查询”不允许联合手术是有办法解决这一单一的查询？
"Union Operation not allowed in sub query" is there a way to fix this in one single query?
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