ComputedField Element (ADF)

Provides a location for defining a computed notification class field.

Синтаксис

<NotificationClasses>
    <NotificationClass>
        ...
        <Schema>
            ...
            <ComputedFields>
                <ComputedField>

Element Characteristics

Characteristic	Description
Data type	None.
Default value	None.
Occurrence	Required once or more per ComputedFields element.
Updates	Can be added and deleted when updating the application.

Element Relationships

Relationship	Elements
Parent element	ComputedFields Element (ADF)
Child elements	FieldName Element for NotificationClass/Schema/ComputedFields/ComputedField (ADF) SqlExpression Element for ComputedField (ADF) DigestGrouping Element for ComputedField (ADF)

Замечания

Computed fields are never stored in the notifications table. Instead, they are computed immediately before the notification data is passed to the content formatter.

Computed fields allow you to make use of the calculation facilities of Microsoft SQL Server. Use of computed fields can improve the performance of your notification application, can reduce the work that you must do in the content formatter, and enables you to use the rich formatting and conversion capabilities in Transact-SQL.

Важно!
If you add or delete a ComputedField element, updating the application deletes and re-creates the notification class to which it corresponds. This includes dropping and re-creating the SQL Server tables used by this notification class. Make sure to back up your application database before updating the application.

Пример

The following example shows a populated ComputedField element. The computed field converts the stock price into a formatted string.

<ComputedField>
    <FieldName>FormattedStockPrice</FieldName>
    <SqlExpression>CONVERT(NVARCHAR(10), StockPrice, 1)
    </SqlExpression>
</ComputedField>

См. также

Справочник

Application Definition File Reference

Другие ресурсы

Функции CAST и CONVERT (Transact-SQL)
Определение схемы уведомления
Обновление экземпляров и приложений

Справка и поддержка

Получение помощи по SQL Server 2005