In this activity, you add documentation to every element in the model, including every column, every table, every constraint, and every trigger.
在这种情况中，你把文档添加到模型的每一个元素中，包括每个列，每个表，每个约束和每个触发器。
In this syntax example, you must either define a new column or define a new table-level constraint.
在这个语法示例中，必须定义一个新列或者定义一个表级约束。
This clause is not allowed if the column is specified in the primary key, or in a unique constraint of the table (SQLSTATE 42831).
如果表的主键或惟一性约束中指定了这个列，那么不允许使用这个子句(SQLSTATE 42831)。
This can take the form of adding a column, changing the data type for a column, adding a constraint, or even deleting a column.
这可以采用添加列、更改列的数据类型、添加约束或者甚至删除列的方式来实现。
If an XML validation check constraint exists on the XML column of the table, the user may need to validate the new XML value before the update either manually or by creating a trigger.
如果在表的xml列上存在XML验证检查约束，在手动更新或者通过触发器更新之前，用户可能需要验证新的xml值。
You probably understand what is meant by a column definition, but you might not understand the idea of a constraint.
您可能理解列定义的含义，但是可能不理解约束的意义。
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NOTnull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。
Now, follow these steps to add a new constraint to check for the existence of a masking method if a column is set as privacy data
现在，添加一个新约束，以便在将一个列设为privacydata时检查是否存在一个masking方法。
SYSCAT.COLCHECKS Contains a row for each column that is referenced by a table check constraint db2 select constname, tabname, colname, usage from syscat.colchecks
COLCHECKS为表检查约束所引用的每个列保持一个行db2select constname,tabname,colname,usage from syscat.colchecks
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。
The column 'CITY' in the OFFICE_INFO nickname is unique and hence a unique constraint has been defined on the nickname OFFICE_INFO on column CITY as follows.
office_info昵称中的列'CITY '是惟一的，因此在列city上定义了昵称OFFICE_INFO的惟一约束，如下所示。
The itemNumber column provides a unique identity for each item (or row) and has an attached column-level constraint that enforces a valid value to always be supplied (NOT NULL).
itemNumber列提供了每个商品（或列）的惟一标识，它上面还有列级约束，强制要求提供正确的值（NOT NULL）。
A check constraint is a type of constraint which can be put on a table column at the time of the creation of the table.
检查约束(checkconstraint)是一类可以在创建表时作用到表列的约束。
The above example creates a check constraint on the column INFO which is of type XML.
以上例子在类型为XML的info列上创建了一个检查限制。
In this case, the DBA can put a check constraint on the XML column and ensure that the application USES one of the pre-registered schemas for validation.
对于这种情况，DBA可以在xml列上放置检查(check)限制，并确保应用程序使用预注册的模式之一执行验证。
Creating a table with check constraint on an XML column.
创建一个xml列包含检查限制的表。
Listing 5. Create check constraint on an XML column.
清单5.在xml列上创建检查限制。
If a NOT NULL constraint is specified, then the column must have a default value other than NULL.
如果规定一个不允许有空值是一个约束，那么字段必须有一个不同于空值的默认值。
A Unique constraint guarantees that there are no duplicates in a specific column and allows you to define a primary key.
唯一约束可以保证在特定的列中没有重复值并允许您定义一个主键。
When you attach a unique constraint to a column allowing null values, you ensure that at most one row will have a null value in the constrained column.
当将唯一约束附加到允许空值的列时，请确保在约束的列中最多有一行包含空值。
Select the column to which the constraint applies in Server Explorer, Database Diagram Designer, or Table Designer.
在服务器资源管理器、数据库关系图设计器或表设计器中选择应用该约束的列。
Delete a unique constraint when you want to remove the requirement for uniqueness for values entered in the column or combination of columns included in the constraint expression.
当希望移除对在约束表达式所包含的列或列组合中输入的值的唯一性要求时，可删除唯一约束。
When you try to assign a data generator to a column that has a unique constraint, the list of available generators displays only generators that can produce unique values.
当您尝试将资料产生器指派给具有唯一条件约束的资料行时，可用产生器的清单只会显示可以产生唯一值的产生器。
If the data that is generated does not satisfy a check constraint on a column, the plan fails when you run it.
如果所产生的资料未满足资料行上的检查条件约束，当您执行计划时会失败。
For example, you might want to create a custom data generator if your database contains a column that has a check constraint that references another column.
例如，如果您的资料库有一个资料行具有参考另一个资料行的检查条件约束，您可能会想要建立自订资料产生器。
Because the Regular Expression generator is not guaranteed to produce unique values, you cannot use it to fill a user-defined type column that has a unique constraint.
由于无法保证规则运算式产生器一定会产生唯一的值，所以您不能使用它来填满具有唯一条件约束的使用者定义型别资料行。
Because the Regular Expression generator is not guaranteed to produce unique values, you cannot use it to fill a user-defined type column that has a unique constraint.
由于无法保证规则运算式产生器一定会产生唯一的值，所以您不能使用它来填满具有唯一条件约束的使用者定义型别资料行。
应用推荐