Question

我最近想出了如何使用VB.Net从SQL Server导出数据作为XML。我使用三个SQL语句并对XPath文档进行维度以将根标记添加到导出：

        Dim connectionString As String
        Dim connection As New SqlConnection
        Dim command As New SqlCommand()

        Dim sql = "select * from scheduledata for xml auto, elements " & _
        "select * from costdata for xml auto, elements " & _
        "select * from csintegrationdata for xml auto, elements "

        connectionString = "Data Source=(localdb)\v11.0; _ 
        Initial Catalog=localACETest;Integrated Security=True"
        connection = New SqlConnection(connectionString)
        connection.Open()

        command.CommandText = sql
        command.Connection = connection
        command.CommandType = CommandType.Text

        Dim xmlRead As XmlReader = command.ExecuteXmlReader()

        Dim xp As New XPath.XPathDocument(xmlRead)
        Dim xn As XPath.XPathNavigator = xp.CreateNavigator()
        Dim xd As New XmlDocument
        Dim root As XmlNode = xd.CreateElement("Data")
        root.InnerXml = xn.OuterXml
        xd.AppendChild(root)

        Dim fStream As New FileStream(Directory, FileMode.Create, FileAccess.ReadWrite)

        xd.Save(fStream)
        fStream.Close()

我希望能够使用VB将这些数据重新导入SQL表中，但是我遇到了一些麻烦。我正在使用的代码是：

        Using sqlconn As New SqlConnection(connectionString)
            Dim ds As New DataSet()
            Dim sourcedata As New DataTable()
            Dim ii As Integer = 0
            ds.ReadXml("C:\Users\coopere.COOPERE-PC\Desktop\Test.xml")
            sqlconn.Open()

            Using bulkcopy As New SqlBulkCopy(sqlconn)
                sourcedata = ds.Tables(0)

                bulkcopy.DestinationTableName = "CSIntegrationData"
                bulkcopy.ColumnMappings.Add("Period", "Period")
                bulkcopy.ColumnMappings.Add("Program", "Program")
                bulkcopy.ColumnMappings.Add("CostControlAccount", "CostControlAccount")
                ...

                bulkcopy.WriteToServer(sourcedata)
            End Using
            sqlconn.Close()
        End Using

执行此操作时，出现错误：System.InvalidOperationException：给定的ColumnName'CostControlAccount'与数据源中的任何列都不匹配。

我认为这是因为导出到XML的表中有一个列满了NULL值，这些值在XML中的任何地方都没有消失。但情况并非总是如此 - 通常会有价值观。

考虑到SqlBulkCopy的列映射无法处理接受空值，如何在导出/导入中处理空值？我也完全接受了不同的路线。

Answer 1

经过多次挖掘，我找到了this link。

作为FOR XML功能的一部分，您可以在最后处理 XSINIL 以处理空值。生成的XML如下所示。

select * from TABLENAME for xml auto, elements XSINIL

<ScheduleWorkPackage xsi:nil="true" />

VB.Net - 将XML批量插入现有SQL Server表

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