Question

当远程数据库中不存在数据行时，是否可以从本地数据库中选择数据行？我写了一个代码，但是不起作用：conlocal是本地数据库连接，而conremote是远程数据库连接； Dim命令为

sqlcommand =  new sqlcommand ("select id from table", conlocal, "where id not in table",conremote)

Answer 1

在线评论

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    'Get ID's from remote database
    Dim RemoteDT As New DataTable
    Using cn As New SqlConnection("Your remote connection string")
        Using cmd As New SqlCommand("Select Id From [RemoteTableName];", cn)
            cn.Open()
            RemoteDT.Load(cmd.ExecuteReader)
        End Using
    End Using
    'Put the Ids into an array
    Dim IdsInRemote As Integer() = RemoteDT.AsEnumerable().[Select](Function(x) x.Field(Of Integer)("Id")).ToArray()
    'Change the array to a single string that can be used in the Select statement
    Dim Remotes As String = String.Join(",", IdsInRemote)
    Dim LocalDT As New DataTable
    Using cn As New SqlConnection("Your local connection string")
        Using cmd As New SqlCommand($"Select Id From [LocalTableName] Where Id Not In ({Remotes});", cn)
            cn.Open()
            LocalDT.Load(cmd.ExecuteReader)
        End Using
    End Using
    For Each row As DataRow In LocalDT.Rows
        Debug.Print(row(0).ToString)
    Next
End Sub

编辑对于版本14（2015）之前的vb.net版本

Using cmd As New SqlCommand(String.Format("Select Id From [LocalTableName] Where Id Not In ({0});", Remotes), cn)

当远程数据库中不存在数据时如何从本地数据库中选择数据

1 个答案: