nullable

美 　英

• 網(wǎng)絡(luò)允許空值；值類型；可空類型

例句

Attribute value with a null reference assigned to a reference type or to a nullable value type.

屬性值等同于分配給引用類型或分配給可為空值類型的空引用。

The result of an arithmetic operator is always nullable, even if the operands are nonnullable and ANSI_WARNINGS or ARITHABORT is set ON.

即使操作數(shù)不可為空并且ANSI_WARNINGS或ARITHABORT設(shè)置為ON，算術(shù)運(yùn)算符的結(jié)果也始終可為空。

Operator defines the default value to be returned when a nullable type is assigned to a non-nullable type.

運(yùn)算符定義當(dāng)可空類型分配給非可空類型時返回的默認(rèn)值。

A type parameter can be constrained to be a reference type, a non- nullable value type, and to have a default constructor .

類型參數(shù)可以約束為引用類型、不可為空值類型和具有默認(rèn)構(gòu)造函數(shù)。

Specifically, any type defined as Nullable(Of T) wasn't allowed to be optional.

特別地，定義為Nullable（OfT）的任何類型都不允許是可選的。

Use nullable types to represent things that exist or do not exist depending on the circumstance.

根據(jù)具體環(huán)境，使用可空類型來表示存在或不存在的事物。

The nullability property of arithmetic operators over floating point data type is always nullable.

對浮點(diǎn)數(shù)據(jù)類型執(zhí)行運(yùn)算的算術(shù)運(yùn)算符的為空性屬性始終可為空。

Assign a value to a nullable type just as you would for an ordinary value type, for example int?

為可以為null的類型賦值的方法與為一般值類型賦值的方法相同，如int？

In this case, define the field to be a nullable type instead of a value type.

在這種情況下，將該字段定義為可空類型而不是值類型。

Though most Rails developers do not like to keep constraints in the database, you should consider things like nullable columns.

雖然大多數(shù)Rails開發(fā)人員都不喜歡在數(shù)據(jù)庫中保留限制，但您應(yīng)該考慮像空列這樣的事情。

The as operator must be used with a reference type or nullable type ('int' is a non-nullable value type).

as運(yùn)算符必須與引用類型或可為null的類型一起使用（“int”是不可為null的值類型）。

You can declare variables and properties with nullable types, and you can declare an array with elements of a nullable type.

可以用可空類型來聲明變量和屬性，也可以用可空類型的元素來聲明數(shù)組。

If there is no default value and the column is not nullable, the server will return an error and an exception will be thrown.

如果沒有默認(rèn)值且列不可為空值，服務(wù)器將返回錯誤，此時將引發(fā)異常。

You can also use the classes and methods of the System. Reflection namespace to generate Type objects that represent Nullable types.

還可以使用System.Reflection命名空間的類和方法來生成表示可以為null的類型的Type對象。

In the lower right part of the section, set all key columns of the output link to non-nullable by selecting No in the nullable column.

在本部分的右下側(cè)，通過選擇空列上的No可將所有輸出鏈接的關(guān)鍵列都設(shè)置為非空。

Indicates whether the current Nullable object is equal to a specified object.

指示當(dāng)前Nullable對象是否等于指定的對象。

Columns in the view select list can be nullable or not nullable.

視圖選擇列表中的列可以為空，也可以不為空。

You store a value in a variable or property of a nullable type in the normal way.

按常規(guī)方式將值存儲在可空類型的變量或屬性中。

Calling GetType on a Nullable type causes a boxing operation to be performed when the type is implicitly converted to Object.

如果對可空類型調(diào)用GetType，則在該類型被隱式轉(zhuǎn)換為Object時將執(zhí)行裝箱操作。

True - then boxing takes place, but only the underlying type that the nullable object is based upon is boxed.

則會發(fā)生裝箱過程，但只將可空對象所基于的基礎(chǔ)類型裝箱。

For this constraint to execute, the foreign key columns must be nullable.

若要執(zhí)行此約束，外鍵列必須可為空值。

If the column is NULLABLE, any number of NULLs can be inserted in that column.

如果此列可以包含NULL值，就可以在此列中插入任意數(shù)量的NULL值。

Therefore you cannot use is to determine whether a variable is a Nullable type.

因此，不能使用is來確定變量是否為可空類型。

If the return type of the method is nullable, the distinguished null value for the type is returned.

如果該方法的返回類型可以為空，則返回類型的突出默認(rèn)空值。

Nullable types are a special case of generic types.

可為Null的類型是泛型類型的特例。

The Nullable class provides complementary support for the Nullable structure.

Nullable類為Nullable結(jié)構(gòu)提供補(bǔ)充支持。

True clears all columns except the declared primary key, nullable columns with no default, and unique key columns.

將清除除聲明的主鍵、沒有默認(rèn)值并且可為空的列以及唯一的鍵列以外的所有列。

Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.

調(diào)用序列的每個元素上的轉(zhuǎn)換函數(shù)并返回可空Int32的最大值。

In this example, no one is allowed to update or insert into that column, which is also marked as unique and not nullable.

在本例中，不允許任何人更新或插入同樣標(biāo)記為唯一和不得為空的列。

There is one major concern regarding this second strategy: in order for it to work, you must set all non-shared columns to NULLABLE.

關(guān)于第二個策略，有一個需要重點(diǎn)考慮的地方：為了讓它工作，必須把所有非共享列設(shè)置為NULLABLE。

The metadata API also provides the ability to define nullable columns, establish primary keys, and set-up relationships between tables.

該元數(shù)據(jù)API還提供了定義可以為空的列的能力，并設(shè)置了表之間的關(guān)系。

ANSI_NULL defaults are always on for ALTER COLUMN; if not specified, the column is nullable.

對于ALTERCOLUMN，ANSI_NULL默認(rèn)值始終為ON；如果沒有指定，列可為空。

The value returned for this column is different from the value returned for the NULLABLE column.

該列的返回值與NULLABLE列返回的值不同。

The expression may be a null value if the parameter is nullable.

如果參數(shù)可為空值，則表達(dá)式可能為空值。

If the target column is not nullable, the insert or update action fails and the user receives an error.

如果目標(biāo)列不可為空，則插入或更新操作將失敗，用戶將收到錯誤消息。

For an example of when you might use a nullable type, consider how an ordinary Boolean variable can have two values: true and false.

有關(guān)可能使用可以為null的類型的示例，請考慮普通的布爾變量如何能夠具有兩個值：true和false。

Nullable types are useful when working with databases and other data structures that may contain elements that contain no specific values.

在使用數(shù)據(jù)庫和其他可能包含未含有具體值的元素的數(shù)據(jù)結(jié)構(gòu)時，可以使用可空類型。

Previously , the code would allow default behavior to occur when handling nullable fields .

以前，代碼允許在處理可為空的域時采用缺省的行為。

If a column is nullable and there is no explicit default value set, NULL becomes the implicit default value of the column.

如果某個列可為空值，并且未設(shè)置顯式的默認(rèn)值，則會使用NULL作為該列的隱式默認(rèn)值。

Correctly generate Update statements for nullable columns.

能夠正確地為可為空的列生成Update語句。