对于优化器不能选择最佳查询执行计划的例外情况，DB 2已经增加了诸如selectivity子句和优化指南之类的特性。
For the exceptional situations where the optimizer cannot choose an optimal query execution plan, DB2 has added features such as the SELECTIVITY clause and optimization guidelines.
因此，您常常可以选择实现只包括在WHERE和ORDERBY子句中引用到的列的索引。
Therefore, you may often choose to implement indexes that include only the columns referred to in the WHERE and ORDER BY clauses.
如果使用标准的into子句，那么按选择的字段的次序填充行。
If you use the standard INTO clause, the row is filled in the order of the selected fields.
WHERE 子句最简单最常见的用法是在选择任意列之前过滤表中的行，如 清单4 所示。
The simplest and most common use of the WHERE clause is to filter the rows from a table before selecting any columns, as demonstrated in Listing 4.
这个更新并不使用SQLwhere子句选择特定的一行。
This update does not use an SQL WHERE clause to select a specific row.
可以使用标量子查询选择将用于where子句的表达式中的特定值。
You can use a scalar subquery to select a specific value that will be used in the expression of the WHERE clause.
您可以通过where子句筛选YQL结果，通过使用子选择来合并或“混搭”来自多个服务的数据。
You can filter YQL results with WHERE clauses, and combine or "mash up" data from multiple services through the use of sub-selects.
可以改变查询的子句，比如它的选择条件、WHERE子句中的选择谓词和ORDERBY子句中的排序条件。
The clauses of the query - such as its selection terms, the selection predicate in a WHERE clause, and ordering terms in an order BY clause - can all be mutated.
当if子句有多个条件时，您可以选择让它在任何条件为true时求值为 true，或者在所有条件都为 true 时才求值为 true。
When the if clause has more than one condition, you can choose to have it evaluate to true when any of the conditions are true or when all of the conditions are true.
在Script窗格中选择任何映射语句，这将显示该语句中所引用的所有源和目标可映射对象，如映射源、循环迭代器、条件、where子句，等等。
Selecting any mapping statement in the Script Pane shows all source and target mappables referenced in the statement, such as mapping source, loop iterator, condition, where clause, and so on.
如果选择的值是Changed，那么只有Key域和要修改的域的原来值会传递到 WHERE子句中。
With a value of Changed, only the Key fields and the original values of the fields that were changed are passed in the WHERE clause.
没有FETCHFIRST(或者类似地，但是并不确切，是没有一个OPTIMIZEfor子句)，那么DB 2毫无疑问会选择其他访问路径。
Without the FETCH FIRST (or similarly, but not exactly, without an OPTIMIZE FOR clause), then DB2 would almost certainly prefer some other access path.
这些操作符选择提供进一步的排序控制，伴随着ORDERBY子句中的给定列出现。
These operator choices provide further sorting control and accompany a given column in the ORDER BY clause.
WHERE子句中的字段决定了数据库将选择的索引。
The columns in the WHERE clause decide what index the database will select.
为此，可以在where子句中将关键字SELECTIVITY放在谓词的后面，后面带一个0到1之间的对选择性的估计值。
To that end, you can append the selectivity keyword right after the predicate in the WHERE clause, followed by an estimated or guessed selectivity value in the range of 0 and 1.
更新3在where子句中使用第二个参数标志来选择要更新的行。
Update 3 also USES a second parameter marker in the WHERE clause to select the row that is updated.
更新子句将确保更新锁定在被选择的行上。
The update clause will ensure that an update lock is held on the selected rows.
在copy子句中选择节点。
注意：这相当于在sql语句的where子句中选择一个数据库列。
Note: This is equivalent to selecting a database column in the where clause of a SQL statement.
DB 2所做的就是允许UPDATE、DELETE和INSERT出现在选择语句的from子句中，并允许用户选择应该从哪个过渡表进行选择。
All that DB2 does is to allow an UPDATE, DELETE, and INSERT to appear in the from clause of a select and allow the user to chose which transition table shall be selected from.
可以在sql语句的where子句中使用它只选择那些对于XPath表达式返回非空xml值的行。
It can be used in the WHERE clause of an SQL statement to select only the rows that return non-trivial XML values for the XPath expression.
更像是SQLwhere 子句中的子选择，但是XQuery语法看起来更直观自然。
This compares more to a sub-select within an SQL where clause, but the XQuery syntax seems more intuitive and natural.
如果不想使某特定列成为GROUPBY子句的一部分，必须在“条件”窗格的“分组依据”列中选择不同的选项以手动更改该设置。
If you do not want a particular column to be part of the Group by clause, you must manually change it by selecting a different option in the Group by column of the Criteria pane.
它是可能的更新和选择使用OUT PUT子句包含单个语句与CTE加入？
It is possible to UPDATE and SELECT in single statement using OUTPUT clause with CTE containing JOIN?
关于表连接的USING和ON子句，哪两句话是正确的？(选择两个)。
Which two statements are true regarding the USING and ON clauses in table joins? (Choose two.)
where子句用于选择行的子集以进行汇总和分组，因此在分组前应用where子句。
WHERE clauses are used to select a subset of rows for summarizing and grouping and are thus applied before any grouping is done.
GROUPBY子句可用在SELECT的多条结果中选择数据并且将数据组织成一列或几列。
The group by clause can be used in a SELECT statement to collect data across multiple records and group the results by one or more columns.
当选择“分组依据”选项或将聚合函数添加到查询中时，所有标记为输出或用于排序的列将自动添加到GROUPby子句中。
When you choose the GROUP BY option or add an aggregate function to a query, all columns marked for output or used for sorting are automatically added to the GROUP BY clause.
当选择“分组依据”选项或将聚合函数添加到查询中时，所有标记为输出或用于排序的列将自动添加到GROUPby子句中。
When you choose the GROUP BY option or add an aggregate function to a query, all columns marked for output or used for sorting are automatically added to the GROUP BY clause.
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