Example 3: Collect catalog statistics on key columns
示例3：收集关键列上的目录统计信息
You must generate data for primary key columns.
您必须为主索引键资料行产生资料。
Example 3 shows how you collect statistics on key columns.
示例3展示如何收集关键列(key column)上的统计信息。
An index with many key columns is called a wide index.
具有许多键列的索引称为宽索引。
The key columns on both the tables cannot be compressed.
两个表中的关键列不能被压缩。
Include foreign key columns as properties on entity types.
包含作为实体类型属性的外部索引键资料行。
Select a slowly changing dimension table and specify its key columns.
选取缓时变维度资料表，并指定其索引键资料行。
We can use randomized index key columns to reduce contention, but at what cost?
我们可以使用随机化的索引键列来减少争用，但这有何代价呢？
Example 4: Collect catalog statistics on key columns and on one column that is not.
示例4：收集关键列上和一个非关键列上的目录统计信息。
Data type of primary key columns, foreign key columns, and columns used on indexes.
主键列、外键列和索引上使用的列的数据类型。
The key columns of an index can include fixed-length and variable-length columns.
索引键列可以包括固定长度和可变长度列。
Common alternatives include clustering index columns or other unique key columns.
常见的替代项包括索引列或其他唯一键列的群集。
The phrase "key columns" means the columns that make up the indexes defined on the table.
短语“关键列(key column)”表示构成表上所定义索引的列。
The columns used in this definition are referred to as the table partitioning key columns.
该定义中使用的列被称为表分区键列。
Copy the primary key columns from each of the other two tables to the junction table.
将其他两个表中的主键列都复制到联接表中。
Run rake db:migrate to create the SUBSCRIPTIONS table and add foreign key columns to SUBJECTS.
运行rakedb:migrate以创建SUBSCRIPTIONS表并将外键列添加到SUBJECTS 中。
These annotations are used to define the composite key columns: "STREET" and "CITY" respectively.
这些注释用于定义组合键列：分别是“STREET”和“CITY”。
In contrast, no checking is performed when records are added to the key columns of a parent table.
与之相反，当记录被添加到父表的键列时，不执行检查。
The key columns are the pi/po (page in/page out), which indicate how many pages have been exchanged.
键值列是pi/po（换进/换出的页面），这表示了对多少页面进行了交换。
For partitioning indexes, it is recommended that you choose key columns that are unlikely to be changed.
对于分区索引，建议选择不大可能改变的键列。
Likewise, the number of key columns and their types will vary, as will the types of the coordinate columns.
同样，键列的数量及其类型以及坐标列的类型也可能不一样。
The T077D table has many columns besides the key columns holding the configuration data for each account group.
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。
Indexes are defined on all primary and foreign key columns to support efficient joins between the 12 tables.
全部主键和外键均定义了索引，来支持12个表之间有效的结合。
A grid that allows the mapping of the columns in the current table to the primary key columns in the mapped table.
一个允许将当前表中的列映射到被映射表的主键列的表格。
Next, select the newly added foreign key constraint in the editor and specify the key columns using the Properties view.
接下来，在编辑器中选择新添加的外键约束，并使用Properties视图指定关键列。
In the path secondary index, the path and node values are key columns that allow efficient seeks when searching for paths.
在PATH辅助索引中，路径值和节点值是用于提高路径搜索效率的键列。
Note that this assumes that key columns are never updated; once a row exists, it is immutably tied to its primary-key value.
注意，这假设从不更新键列；一旦一行存在了，它的主键值就不变了。
The best practice is to have many columns in a row, as opposed to linking different rows across different tables via key columns.
相对于通过键列跨不同的表链接不同行，最佳实践将是在一行中有许多列。
After an XMLToSQL is created, primary key columns and target columns are set. The following sample class illustrates these steps.
XMLToSQL创建完后，就可以设置主键列和目标列了。
In the lower right part of the section, set all key columns of the output link to non-nullable by selecting no in the nullable column.
在本部分的右下侧，通过选择空列上的no可将所有输出链接的关键列都设置为非空。
应用推荐