Question

我在从表中获取最后id的值时遇到问题。

由于加载整个列会在将来给我一个问题（DataTable有其限制）所以我决定寻找另一个解决方案，但我没有运气让它工作。< / p>

我有字符串命令，但我不知道存储返回值的位置。这是我的代码：

        Dim query As String = "SELECT MAX(id) AS LastId FROM Table1"
    Dim dtmain As New DataTable
    Try
        With sqlcmd
            .CommandText = query
            .Connection = sqlcon
        End With

        With sqladp
            .SelectCommand = sqlcmd
            .Fill(dtMain)
        End With
        MsgBox("last id = " & dtmain.Rows(0)("LastId"))
    Catch ex As Exception

    End Try

我什么都没得到，而msgbox甚至没有表现出来。

注意：我希望表中的最后一个id和 NOT 插入的id。

这是我的参考和声明：

   Imports System.Data.OleDb
    Private conn As OleDbConnection
    Private adapter As OleDbDataAdapter
    Private cmdd As OleDbCommand

我还在项目参考

中添加了Microsoft ADO Ext 2.8 for DDL and Security

Answer 1

如果您的数据来源位于当前数据库中：

Dim dbConnect As Database
Dim rstRecordset As DAO.Recordset

Set dbConnect = Access.CurrentDb

Dim query As String = "SELECT MAX(id) AS LastId FROM Table1"

Set rstRecordset = dbConnect .OpenRecordset(query)
MsgBox("last id = " & rstRecordset.Fields(0).value & ""))

dbConnect.Close
Set dbConnect = Nothing
Set rstRecordset = Nothing

如果您的数据来源位于另一个Access数据库中：

Dim cnnConn As ADODB.connection
Dim rstRecordset As ADODB.Recordset
Dim cmdCommand As ADODB.Command

' Open the connection.
Set cnnConn = New ADODB.connection
With cnnConn
    .ConnectionString = _
        "Provider=Microsoft.Jet.OLEDB.4.0"
     .Properties("Jet OLEDB:Database Password") = "pass"
     .Open "D:\Databases\Database.mdb"
End With

' Set the command text.
Set cmdCommand = New ADODB.Command
Set cmdCommand.ActiveConnection = cnnConn
With cmdCommand
    .CommandText = "SELECT MAX(id) AS LastId FROM Table1"
    .CommandType = adCmdText
    .Execute
End With

' Open the recordset.
Set rstRecordset = New ADODB.Recordset
Set rstRecordset.ActiveConnection = cnnConn
rstRecordset.Open cmdCommand
MsgBox("last id = " & rstRecordset.Fields(0).value & ""))

' Close the connections and clean up.
cnnConn.Close
Set cmdCommand = Nothing
Set rstRecordset = Nothing
Set cnnConn = Nothing

在vbnet中加载SELECT MAX（id）的位置

1 个答案: