这些表达式是使用函数构成的，结合这些函数来得到我们可能要查找的结果。
These expressions are formed using functions, which are combined to get the results we may be looking for.
注意：优化器不会对下面这个查询使用函数索引。
Note: Here is a query for which the optimizer cannot consider using the functional index.
最后，执行查询，该查询将使用函数索引。
您可以使用函数abs和arg获得绝对值和辐角。
You can use the functions abs and arg to obtain the absolute value and the argument.
在本文中，您将了解如何在php中明智地使用函数。
In this article you'll see how to use functions in PHP wisely.
另一使用函数式技巧的地方是SpinWait对象。
Another place where functional techniques are being used is the SpinWait object.
因此可以通过组合使用函数来实现累积的效果。
Functions can also be combined to achieve cumulative effects.
这个例子演示了如何使用函数索引选择具有某些特征的图像。
This example demonstrates how functional indexes can be used to select images with certain characteristics.
要使用函数性语言，只需要放弃命令式编程的风格。
To use a functional language, you just need to let go of imperative programming styles. Learning to write in a more functional style has several benefits.
每次使用函数或者测试时，必须依照所计数列对数据集进行排序。
Each time you use such a function or test, the data set must be sorted by the counted column before the occurrences of the values can be counted.
然后，您可以将库装入到您的地址空间中并使用函数指针调用方法。
You could then load the library into your address space and call the methods using function Pointers.
因为Versa大量使用函数，它有时给人一种类LISP的感觉。
Because Versa USES functions heavily, it sometimes has a LISP-like feel.
应当详细解释定制函数，便于表单设计人员正确地选择并使用函数。
You should explain your custom function in detail so that the form designer can choose and use the function correctly. The following is an example of the help method.
在这种情况下，请查看PHP是否支持此功能并且使用函数或扩展替代它。
In such cases, look into whether PHP itself supports the feature and use that function or extension instead.
这比使用函数边界实用得多，函数边界提供的范围可能太大或太小。
These are more practical than using the function boundaries which may provide too much, or too little, scope.
实现这种功能最常用的方式是根据可用的语言特性使用函数组合技术。
The most general way of approaching this is by using techniques of function composition according to available language features.
希望我们介绍的这些创建和使用函数索引的方法能够帮助您改善查询搜索的性能。
Hopefully by seeing the various ways that functional indexes are created and used, you will be able to use them to improve the performance of your query searches.
通过将使用函数和方法作为高阶函数进行开发，可使应用程序更加健壮。
By developing utility functions and methods as higher-order functions, you make your applications more robust.
另外，这些函数还常用于定义视图，让应用程序使用视图，而不是直接使用函数。
Another popular use of these functions is to actually use them in the definition of a view and have applications use the view instead of using the function directly.
本文假设您已经具有一些使用PHP的经验，并能够使用函数来传递变量并返回结果。
This article assumes that you have some experience using PHP already and can use a function to pass a variable and return a result.
如果表非常小，或者不经常执行使用函数索引的查询，那么创建函数索引可能收效甚微。
If the tables are small or if the frequency of queries that would make use of the functional index is small, then you may not benefit from creating a functional index.
对于每个特别的日期，脚本都要使用函数weekday (i)确定它是哪个工作日。
For each particular date, the script identifies which day of the week it is, using the function Weekday (I).
本文中的例子使用的是面向对象的风格，但使用函数式方式可以获得同样的结果。
The examples in this article use the object-oriented style, but you can obtain the same results using a functional approach.
此决策实际取决于优化枚举器之前如何使用函数以及应如何对函数进行大量测试。
This decision really depends on how the function is used and should be heavily tested prior to optimizing the enumerator.
要想在bashshell脚本中使用函数，可以使用清单26 所示的方法。
To use a function within your bash shell script, you use the methods shown in Listing 26.
此外，您还将了解如何创建和使用函数索引，以及在创建函数索引之前需要考虑的一些问题。
In addition, you will learn how to create and use functional indexes and be given a list of things to consider before creating functional indexes.
接下来将深入讨论如何创建和使用函数索引，以及如何生成和检验查询计划，并提供具体的示例。
The in-depth discussion and examples that follow explore creating and using functional indexes and how to generate and examine query plans.
在使用函数来收集数据时，如果不首先以某种方式对收集的数据进行处理，那么它们将会是无效的。
When using this function to gather data, some of the raw data collected will not be useful without first processing it in some way.
这是使用函数闭包在函数定义中封闭变量的第一种方法，但不是惟一的方法，目前就采用这种方法。
This is your first opportunity to use function closures to enclose variables in function definitions, but it won't be the last, so get used to this, too.
Python中有多种可实现重用的途径，但最简单的技术莫过于使用函数，也称为方法或子例程。
In Python, there are many ways to do this, but the simplest technique is to use functions, which also are known as methods or subroutines.
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