The optimizer calculates and compares the costs of each join method and selects the best one to use when evaluating query execution plans.
当评估查询执行计划时，优化器计算并比较每种连接方法的成本，然后选择要使用的最佳方法。
To show how to interpret SET EXPLAIN output for star join plans, we use the same example query as before.
我们使用前面的同一个示例查询来说明如何解释星型连接计划的SETEXPLAIN输出。
A star join query typically involves a fact table and several dimension tables, with join predicates between the fact table and each dimension table.
一个星型连接查询通常包含一个事实表和几个维度表，事实表和每个维度表之间都有连接谓词。
You can always convert a nested query into an equivalent join.
您始终可以将嵌套查询转换成等价的连接。
In these cases you can query the object representing the advised join point for its associated annotations.
在这种情况下，可以查询表示已通知连接点的对象来获得相关的注释。
The nested loop join method is used to join the remote query result from each warehouse and the XML composite view result.
这里使用了嵌套的循环连接方法来连接来自每个仓库的远程查询结果和xml合成视图结果。
Figure 4 shows a plan using the nested loop join operations at the federated server to evaluate this query.
图4展示了一个在联邦服务器使用嵌套循环连接操作符来计算这个查询的计划。
You can define guidelines that influence only a few attributes of an execution plan, such as index specification for a certain table in the query or join order for a pair of tables.
可以定义那些只影响执行计划的某些属性的准则，比如查询中的某个表的索引说明，或者一对表的连接顺序。
Using views in a SELECT statement can restrict the join order of the tables and limit the query optimizer's choices when considering access plans.
在select语句中使用视图，可以限制表的连接顺序，同时也限制查询优化器在考虑访问计划时的选择。
All the new star join directives are query level directives that affect the execution of a query.
所有新的星型连接指令都是查询层次的指令，会影响查询的执行。
Join plan directives that force optimizer to use the designated join method to join tables in the query, either nested loop join, sort merge join, or dynamic hash join.
连接计划指示，强制优化器使用指定的连接方法来连接查询中的表，要么是嵌套循环连接、分类合并连接，要么是动态哈希连接。
If specified, it can only take the value 'TRUE' to indicate that the given table must be the first table accessed in a join query.
如果指定了的话，它将只接受“TRUE”值，表示给定表必须是连接查询中进行访问的第一个表。
The third part is of vital importance in query tuning, because it provides us with a great deal of useful information, such as the data access method and the join method that the query used.
第三部分对于查询调优是至关重要的，因为它提供了大量有用的信息，例如查询所用的数据访问方法和连接方法。
In the query access plan shown in Listing 9, notice a join between the table EMPLOYEE and a table function, GENROW.
在清单9所示的查询访问计划中，要注意表employee和一个表函数GENROW间的一个连接。
The optimizer would chalk out a query plan before performing the actual join operation itself by making use of the statistical data.
在执行实际的连接操作之前，优化器使用统计数据制定一个查询计划。
The following query explicitly casts both sides of the join predicate to DOUBLE.
以下查询明确地将连接谓词的两端转换为DOUBLE。
Often the join order of a query will greatly determine the query execution performance, since it is more efficient to filter rows as early as possible.
通常，查询的连接顺序很大程度上决定了查询的执行性能，因为越早地过滤行，效率越高。
In addition, DB2 can leverage new query and join operators, as well as new index processing techniques, to provide strong runtime performance for queries involving XML documents.
另外，DB 2可以利用新的查询和联结操作符以及新的索引处理技术，为涉及XML文档的查询提供更好的运行时性能。
The disadvantage is that there are more tables to join in building a query, and users are less likely to use them.
其缺点是在构建查询时需要更多的表加入，而且用户不喜欢使用。
The output of our disconnected JoinRowSet object correctly parallels the data we obtained when we performed our server side database JOIN query (compare to Table 3).
非连接对象JoinRowSet的输出与我们在服务器端执行join查询得到的数据完全一致(与表3比较)。
Query after removing useless join operations.
删除无用的连接操作之后的查询。
Query 2 applies the join predicate to the authors table.
查询2对authors表应用连接谓词。
Example 5: INLIST to Nested Loop Join (query rewrite).
例子5：INLIST改为嵌套循环连接(查询重写)。
XPath doesn't provide a means to join XML nodes in a query.
XPath没有提供在查询中连接xml节点的方法。
The optimizer can choose a star join plan only if a query involves tables from a star or snowflake schema that meets the following requirements.
只有查询中包含满足以下要求的星型或雪花模式的表时，优化器才可以选择星型连接计划。
This query performs an outer join to compare the sales information for 10 particular stores for January and November.
这个查询会执行一个外连接操作，以便比较从 1 月份至 11 月份的10 个特殊商店的销售信息。
The optimization of SQL queries utilize sophisticated features, such as: query rewrite, multiple join methods, detailed statistics, parallelism etc.
SQL查询的优化利用了一些复杂的功能，例如：查询重写、多连接(join)方法、详细的统计、并行性等。
If the query includes a join, the optimizer must determine the join plan (hash, sort merge, or nested loop), and the order in which tables are evaluated or joined.
如果该查询包含了连接，那么优化器就必须确定连接计划(hash、sortmerge或nestedloop)，以及评估或连接表的次序。
For example, the query in Listing 1 describes a join of the Dept and Employee tables.
举例来说，清单1中的查询描述了Dept和employee表的连接。
Joins referenced by the cube model object, which join the dimensions in the query to the facts object.
将查询中的维联结到事实对象的多维数据集模型对象引用的联结。
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