Constraints Supports, primary, foreign, unique, not null constraint.
约束支持主键、外键、惟一和非空约束。
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。
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。
If the form input field is not null, set the payload you receive as the widget value, as shown in Listing 14.
如果表单输入字段不为空，将小部件的值设为接收到的负载，如清单14所示。
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。
Usage: This parameter controls whether or not null data values are treated as zeros when used in calculations.
用法：该参数控制在计算中是否将null数据值看作0。
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。
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。
For instance, I could write a validation rule asserting that a given parameter was not null and then reuse it across all methods needing the same rule.
例如，我可以写一个验证规则，用于断言指定参数不为null，然后在所有需要同样规则的方法中重用它。
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。
For example, if you are creating a Customer table and the CustomerID is marked as not null, then when you define the primary key, CustomerID will show as a candidate column.
例如，如果您要创建一个Customer表并且CustomerID 被标记为not null，则当您定义主键时，CustomerID将会显示为备选列。
If the value of the transportTModelKey parameter is not null, then a transport categorization keyedReference is added; its value is the value of the transportTModelKey parameter.
如果transportTModelKey参数的值不为空，就添加一个传输类别 keyedReference ；它的值即是 transportTModelKey 参数的值。
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)。
The uniqueness is ensured on the NOT NULL values.
确保NOT NULL 值的惟一性。
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。
The "name" column will be a CHAR (30), set to NOT NULL, and have a unique index on it.
“name”列的类型是CHAR(30)，不允许为空，而且根据此列建立了一个索引。
Partition compatibility is not affected by columns with not NULL or FOR BIT DATA definitions.
分区兼容性不受带有NOT NULL或FORBITDATA定义的列的影响。
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。
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。
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。
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。
Though you did not specify that column, the Rails migration created it for you anyway, with auto_increment and not NULL.
虽然没有指定这个列，但是Rails迁移会自动创建它，并具有auto_increment和NOT null属性。
When a unique index is created on a column in Oracle 10g, it ensures that the NOT NULL values entered in that column are unique.
当在Oracle10g中的列上创建UNIQUE索引时，会确保此列中输入的NOT null值是惟一的。
After a quick test of your new structure (namely, it's not NULL), continue to make the call using the call_usermodehelper_exec function.
快速测试新结构(即，非null)后，使用call_usermodehelper_exec函数继续调用。
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。
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。
You can also use the system catalog views to retrieve information about NOT NULL, unique, primary key, foreign key, and table check constraints. For example.
也可以使用系统编目视图来检索关于NOT NULL、惟一、主键、外键和表检查约束的信息。
The NOT NULL attribute of column Credit_Line in table ACCOUNT has to be dropped because some other account types have been added that do not have a credit line.
ACCOUNT表中的 Credit_Line列的NOT NULL属性必须删除，这是因为添加了没有信用行的其他账号类型。
A workaround to this is to supply a default value to the not NULL column whose value comes from a BEFORE INSERT TRIGGER, so that the constraint is not violated.
一种解决方法是给从BEFORE INSERT触发器取得值的NOT null列提供默认值，这样就不会违反约束。
In Oracle 10g, if there is a BEFORE INSERT TRIGGER and a NOT NULL constraint on a table, then the BEFORE TRIGGER is executed first, and then the constraint check is performed.
在Oracle10g中，如果表上同时存在BEFORE INSERT触发器和NOT NULL约束，那么先执行BEFORE触发器，然后执行约束检查。
应用推荐