空值

这个标记通常称作空值（nullvalue）、空列表（nulllist）或者空指针（nullpointer）。

This marker is usually called the null value , the null list , or the null pointer .

本文在空值环境下的NFD，NMVD强、弱保持条件及相应的推导公理的基础上，讨论了空值环境下的连接依赖的强、弱保持成立的条件及相应的定理。

In this paper , the tenable condition of the strong and weak holding of join dependency under null value circumstances and the relevant theorems are discussed .

如果没有year元素，则调用返回一个空值。

If there is no year element , then the call will return null .

空值和N关系代数

Nulls and N-Relational Algebra

它附加一个NULL字符以使字符串行包含一个正确的以空值终止的C字符串。

It appends a NULL character so that line contains a properly null-terminated C string .

rev元素的via子元素包含一个空值。

The via subelement of the rev element contains an empty value .

如果这些参数不是空值，Portlet将自动接收它们。

The portlet will automatically receive these parameters if they are not null .

否则，Shell将把尾随文本解释为变量名称的一部分&并且很可能返回一个空值。

Otherwise , the shell interprets the trailing text as part of your variable name & and most likely returns a null value .

这种做法会捕捉忘记使用参数的情况（由于required=“yes”元素），并传递空值或多个值。

Doing so traps forgetting the parameter ( because of the required = " yes " element ) and passing empty or multiple values .

在Java中，当引用类型没有引用任何对象时将其赋空值，这是公共的操作。

In Java , it is a common practice to assign a null value to a reference type when it is not referencing any object .

空值环境下关系模式到（N）BCNF无损连接分解

Decompositions for Relational Schema Under Null Value Circumstances Into BCNF With Lossless Joins

这就意味着一个User在创建时必须具有一个相关的Organization（如果Organization是可选的，那么您就应该使用一个可以为空值的hasone关系）。

This means that a User must have an Organization associated with it when it is created ( if the Organization was optional , you would use a nullable has_one relationship instead ) .

这个例程使用了cdeclC声明调用约定，并返回空值。

This routine uses the __cdecl C declaration calling convention and returns void .

空值环境下（N）4NF、（N）5NF的研究

Research on ( N ) 4NF ,( N ) 5NF Under Null Value Circumstances

空值（NULL值）是关系数据库中的一个重要概念，我们可以利用空值进行数据查询。

" NULL " Value is a important concept of visual FoxPro , we can use " NULL " in looking for data .

空值环境下模板依赖（NTD）的研究

Research of Template Dependency ( NTD ) Under Null Value Circumstances

首先，None是一个你可以理解为“没有值”或“没有赋值”或者“空值”。

First , None is a special object you can use to mean " no value " or " unknown " or " not set " or " null " .

然后，代码通过检索用户名和密码的DOM元素并将它们的值设置为空值来模拟输入空用户名和密码。

The code then simulates entering an empty user name and password by retrieving their DOM elements and setting their values to empty values .

RPG使用一个1字符字段（比如一个指示符）来确定列是否包含空值。

RPG uses a1 character field ( like an indicator ) to determine if a column contains nulls .

基于空值数据库的T-SQL语言研究

Research on T-SQL in Relational Database with Null Values

如果validator属性有一个非空值，则生成的代码中会包括一个JavaScript表达式，以决定是否可以进行远程调用。

If the validator attribute has a non-empty value , the JavaScript expression is included in the generated code to decide whether the remote call can be made or not .

本文在多环境下对空值NULL的设置、赋值、判断及其编程处理方法进行了讨论和分析，并给出了一些明确的结论和使用建议。

This text discussed and analyzed the method to set up , to judge and to endow value to the empty value " NULL " and carried out the method to project in multi environments .

在DB2fori6.1发布之前，SQLUpdate和Insert语句能够使用一个值为-1的指示符变量，将支持空值的列设置为空值。

Prior to the DB2 for i6.1 release , SQL Update and Insert statements could use an indicator variable with a value of-1 to set a null capable column to the null value .

JSON支持除对象之外的各种数据类型：字符串、空值、数字（整数或实数）、布尔值和数组（包含在方括号中的逗号分隔的值序列）。

JSON data supports various data types besides objects : strings , null values , numbers ( integer or real ), Boolean values , and arrays ( comma-separated sequences of values enclosed in square brackets ) .

下一步，指定一个空值，因为您没有为此图像添加PDF链接（通过AddLink方法创建）目标。

Next , specify a null because you 're not adding a PDF link ( created with the AddLink method ) target for this image .

空值环境下广义连接依赖（NGJD）及推导规则的研究

Research of Generalized Join Dependency ( NGJD ) and Its Inference Rules Under Nun Value Circumstances

dataStore中是空值，默认情况下单元格中显示“undefined”，它将作为空字符串（无数据的单元格）重新呈现。

The null values in the dataStore , which would by default show up as cells with the word " undefined " displayed inside , are re-rendered here as empty strings ( cells with no data ) .

“ustlowts”是空值，这说明了没有再次对该表进行这一统计。

" ustlowts " is null , which indicates that statistics have never been run against this table .

因为在当前的应用中并未采用身份认证，此时执行remoteUser检索将会返回空值。

Because there is no authentication currently set in your application , performing a retrieving the remoteUser at this point will return null .

本文首先基于M.Arenas等人给定的XML中DTD和XML树的定义，提出空值、不完全树元组等概念，在此基础上，给出弱函数依赖及其满足性的定义；

In this paper , first , based on the definitions of DTD and XML tree given by M.Arenas et al . , concepts of null value , incomplete tree tuple are proposed , based on it , the definition of weak functional dependency and its satisfaction are given ;