两个或多个子项内引用的不同列组
Different sets of columns referenced in two or more subterms
有时候，列组或类似的统计选项会很有用。
Sometimes, column group, or like statistics options can be useful.
制冷管排列形成列组18。
示例19：收集捕获了列组的目录统计信息。
Example 19: Collect catalog statistics that capture column groups.
列组的使用将给多个谓词的联合选择提供更准确的估计。
The use of column groups provides more accurate estimates of the joint selectivity of multiple predicates.
这个例子解释说明了列组统计信息对一个合格的OR谓词的影响。
This example illustrates the effect of column group statistics on a qualifying OR predicate. Consider the following query on the EMPLOYEE table.
收集单个列的统计数据还不足以提供所需信息，因此您需要收集列组统计数据。
Collecting statistics of individual columns may not be enough to provide the information required, so you need to collect column group statistics.
这些电动车组是按欧洲铁路通用性规定设计的目前世界上最现代的高速列组。
They currently represent the most modern high speed trains in the world and are designed in strict compliance with the regulations now governing European interoperability.
列组(ColumnGroup)统计信息将获得一组列的不同值组合的数目。
Column group Statistics obtains the number of distinct combinations of values for a group of columns.
下列例子说明了如何使用RUNSTATS收集捕获了列组信息的目录统计信息
The following example illustrates using RUNSTATS to collect catalog statistics that capture column group information
本例中，总共有两个列组：(deptno,deptname)和(admrdept,location)。
In this case, there are two column groups: (deptno, deptname) and (admrdept, location).
在没有列组统计信息的情况下再次收集统计信息的话，优化器会选择一个类似如下所示的查询访问计划，它的基数估计值为2。
A query access plan similar to the following is chosen by the optimizer, with a cardinality estimate of 2.
在没有列组统计信息的情况下再次收集统计信息的话，优化器会选择一个类似如下所示的查询访问计划，它的基数估计值小于2。
A query access plan similar to the following is chosen by the optimizer, with a cardinality estimate under 2.
这两组列都可以编制索引，但是使用不同的索引。
Both sets of columns may be indexed, but by different indexes.
借助这个特性，数据管理员可以在表的列和行级别控制用户和组的读写访问。
Using this feature, data stewards can control read and write access for users and groups at the table column and row level.
有时，页面或片段都是纯静态的，比如一列状态或一组经常问到的问题。
Sometimes, pages or fragments are purely static, such as a list of states, or frequently asked questions.
T077D表除了保持每个账户组的配置数据的关键列以外还有许多的列。
The T077D table has many columns besides the key columns holding the configuration data for each account group.
可在整个列上计算聚合，或者由作为函数的第二个参数所给出的分组列指定的子组上计算聚合。
You can compute aggregations on the whole column, or on subgroups that are specified by the grouping column given as the second parameter of the function.
它应该返回两个列，第一列中包含用户名，而第二列中包含组名。
It should return two columns, the first holding a username and the second holding a group name.
表的一个通用模式是每一列包含一组重复的单元格。
The generalized pattern across the table is that each column contains a repeating group of cells.
因此，随机化的列可以减轻一组相似值或序列值的争用问题，但对于相同的值没有帮助。
Therefore a randomized index column can relieve contention problems for sets of similar or sequential values, but it's no help with identical values.
记录或行包含一组包含了数据的字段或列。
A record or row contains a set of fields or columns containing data.
可以为单个列或一组列修改频率和分位数统计信息的精确度。
The precision for the frequency and quantile statistics can be modified for an individual column or a group of columns.
分区键是用于确定特定一行数据存储在哪个分区的一个列(或一组列)。
A partitioning key is a column (or group of columns) that is used to determine the partition in which a particular row of data is stored.
如果基于查询工作负载选择一个分区键，那么此分区键通常应该包含一个合并列或常被用于很多查询的一组列。
If you choose a partitioning key based on your query workload, the partitioning key should typically consist of either a joined column or a set of columns that is frequently used in many queries.
如果有，它们将在左边的列中这个组下使用单词permission来描述。
If there were, they would be described below the group with the word PERMISSION in the left column.
随后rdf应用程序所要操作的就是清单2中显示的这列三元组了。
It is the list of triples shown in Listing 2 that is then acted on by RDF applications.
最后两列显示了CPU成本和相应的执行组地址空间的收集开销。
The last two columns show the CPU cost and collection overhead for just the Execution Group address space.
模板由关于数据库的模式信息、一组表、列属性和标识行的主键构成。
A template consists of schema information about a database, a group of tables, column attributes, and the primary keys that identify rows.
模板使用关于数据库的模式信息、一组表、列和主键定义一组主副本和一个副本集。
A template USES schema information about a database, a group of tables, columns, and primary keys to define a group of master replicates and a replicate set.
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