This mechanism has the benefit of limiting repeated conditionals testing for certain constraints, such as collection sizes or the previously discussed not-null condition.
这种机制具有限制针对特定约束条件的重复条件测试的好处，如集合大小或之前讨论过的非null的情况。
If not NULL, increment the line counter.
如果不是NULL，则增加行计数器。
These instance variables are not reset and, if they are not null, are used to provide the username and password on every request.
这些实例变量不能重新设置，如果它们不为空，则用于为每个请求提供用户名和密码。
We added the NOT NULL flag to indicate that the fields must not be null.
我们添加了NOT NULL标志来指示字段必须不能为空。
This new validation will enforce NOT null column constraints by rejecting null values, but only in situations where your database would reject a null value.
这种校验会通过拒绝空值，强迫加上非空[not NULL]字段的约束，但是也只有在这种情况下，你的数据库会拒绝空值。
Constraints Supports, primary, foreign, unique, not null constraint.
约束支持主键、外键、惟一和非空约束。
The combined record is much easier to use-you only have to check the PICTURE field to see if it's not null (which was the result of the LEFT OUTER JOIN).
而组合的记录使用起来要容易得多—只需检查PICTURE字段，查看它是否为空(这是LEFTOUTER JOIN的结果)。
In lines 22 through 34 you select an operating system that is not NULL from the list obtained in previous step.
从第22行到第34行从上一步中获得的数组中选择一个不为空的操作系统。
If the input binding parameter is not NULL, then it means that the endpoint resides on a remote host.
如果输入绑定参数不是NULL，就意味着端点在远程主机上。
Some constraints will not change (not null, maximum length in the database), but some will vary with the country.
一些约束不会有变化（非空、数据库中的最大长度），但有一些会因国家而不同。
Similarly, the thread local password is checked and used if not null (and reset to null after use.)
类似地，仍将检查线程本地密码，如果不为空，则使用它(并且在使用后重新设置为空)。
Application of data to targets: Replication requires columns of like attributes (for example, INTEGER NOT NULL from the source table to INTEGER NOT NULL at the nickname).
到目标的数据应用：复制需要像属性一样的列(例如，从源表的INTEGERNOT NULL到别名上的INTEGER NOT NULL)。
The first one asserts that the calculator instance object is not null, i.e. it exists.
第一个宣称这个计数器实例对象不是空，就像它实际存在一样。
Before using objects like rows and cells, be sure to test them to make sure they are not null.
在使用行和单元格这样的对象之前，一定要测试它们，确保它们不为空。
One more important note: in the following lines of code from Listing 7, broken out in Listing 8 below, the code tests each cell to make sure it's not null.
还有一个重点需要注意：在清单7中的以下代码行(在下面的清单8中断开)中，这段代码测试每个单元格，确保它们不为空。
The unit test methods first verify that the object provided is not null, and then perform one or more very basic actions on the object.
单元测试方法首先验证所提供的对象不是空的，然后对该对象执行一个或多个非常基础的操作。
If the customer number is not null, that is, the customer is already known, the left hand path is followed (2), and the customer data is retrieved from the customer registration service (3).
如果客户编号不为空，即客户是已知客户，则遵循左侧的路径(2)，并从客户注册服务中检索客户数据(3)。
For primary and unique keys, only the not null columns are listed and can be selected to define these keys.
对于主键和外键，只有非空列才能被列出和选择来定义这些键。
Initially, this routine checks if the passed inquiry context is not NULL and is for a group member inquiry.
这个例程首先检查传递的查询上下文是否非null，以及是否是用于组成员查询的上下文。
One of the problems with not entering this data in regular RDBMS columns is that no rules are defined-no data types, not NULL identifiers and so forth.
未在常规的RDBMS列中输入该数据导致的问题之一是没有定义任何规则——没有数据类型和NOT NULL标识符等。
Sometimes you may want to change this order or perhaps only specify values for columns that have NOT NULL constraints.
有时候您希望更改这种顺序或可能希望只为具有NOT NULL约束的列指定值。
This column should be NOT NULL, and will have no business meaning.
这个列应该是NOT NULL，并且没有商业意义。
By default, a column can contain a NULL value, but if you don't want that, you can append the "NOT NULL" postfix to the field definition.
默认情况下，列可以包含null值，但是，如果不想这样，可以在字段定义中附加“NOT NULL”后缀。
If defined as NOT NULL, the value corresponds to the start time associated with the most recent transaction (the value of the as ROW BEGIN column).
如果定义为NOT NULL，该值会对应于与最近的事务相关联的开始时间(ASROW begin列的值)。
For example, if a before trigger supplies value to a NOT NULL column, then the before trigger is executed first and a value is supplied to the column so that the NOT NULL constraint isn't violated.
例如，如果一个BEFORE触发器给一个NOT null列提供值，那么先执行BEFORE触发器，给列提供值，所以不会违反NOT NULL约束。
So in the example above, the NOT NULL constraint would get violated, and the INSERT statement would error out.
因此，在上面的示例中，会违反NOT NULL约束，INSERT语句会出错。
But in DB2, you must provide a value for NOT NULL columns in an INSERT statement when a default hasn't been defined.
但在DB 2中，如果未定义该值，则必须在insert语句中为NOT null列提供值。
The portlet will automatically receive these parameters if they are not null.
如果这些参数不是空值，Portlet将自动接收它们。
The uniqueness is ensured on the NOT NULL values.
确保NOT NULL 值的惟一性。
The uniqueness is ensured on the NOT NULL values.
确保NOT NULL 值的惟一性。
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