id name

Question

这是我的数据库表

id name

1 abc
2 xyz
它输入1然后各自的值“abc”显示在不同的文本框???

Private Sub butsea_Click(sender As Object, e As EventArgs) Handles butsea.Click

    Dim dset As New DataSet
    Dim da As SqlDataAdapter
    Dim myCmd As New SqlCommand

    Try
   myConn.ConnectionString = "Data Source=THEONE\PARTH;Initial Catalog=testdatabase;Integrated Security=True;"
        myConn.Open()

        Dim avalue As String = (InputBox("Input Student Id", "Search Student")).ToString
        txt_id.Text = avalue
        da = New SqlDataAdapter("SELECT * FROM studentdetails where student_id= '" & txt_id.Text & "", myConn)
        If dset.Tables(0).Rows.Count > 0 Then
           'what should i write here
        Else
            MsgBox("No Record Found")
        End If

    Catch ex As Exception
        MsgBox(ex.Message)
    Finally
        myConn.Close()
    End Try

End Sub

Answer 1

如果你只需要获取一个值 - 使用DataAdapter和DataSet是过度的。使用SqlCommand.ExecuteScalar方法并在查询中代替“SELECT * ...”执行“SELECT YOURFIELD ...”。

这样你就不必跳过建立数据集的箍，检查行数等，而只是检查Nothing的返回值。

更新以下是您修改为使用ExecuteScalar的代码

Private Sub butsea_Click(sender As Object, e As EventArgs)  Handles butsea.Click

        Dim myCmd As SqlCommand
        Dim myConn As New SqlConnection
        Dim oResult As Object

        Try
            myConn.ConnectionString = "Data Source=THEONE\PARTH;Initial Catalog=testdatabase;Integrated Security=True;"
            myConn.Open()

            Dim avalue As String = (InputBox("Input Student Id", "Search Student")).ToString
            txt_id.Text = avalue

            myCmd = New SqlCommand("SELECT student_name FROM studentdetails where student_id= '" & txt_id.Text & "'", myConn)
            oResult = myCmd.ExecuteScalar()

            If oResult IsNot Nothing Then
                txt_name.text = oResult.ToString
            Else
                MsgBox("No Record Found")
            End If

        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            myConn.Close()
        End Try
End Sub

此代码假定您需要显示的数据库字段名为student_name，并且您将名为txt_name的TextBox添加到表单中。

Answer 2

您需要为要显示的每个字段添加其他文本框（例如，名为txtStudentName的文本框可用于名称，依此类推，用于表studentdetails中的其他字段。）

查询数据库的正确方法（省略其他方法，如使用SqlDataReader）应该是以下

  Dim dset As New DataSet
  Dim da As SqlDataAdapter

Try
    myConn.ConnectionString = "Data Source=THEONE\PARTH;Initial Catalog=testdatabase;Integrated Security=True;"
    myConn.Open()
    Dim avalue As String = (InputBox("Input Student Id", "Search Student")).ToString
    txt_id.Text = avalue

    ' prepare the adapter with a commandtext. Do not use string concatenation from user input'
    da = New SqlDataAdapter("SELECT * FROM studentdetails where student_id=@id", myConn)
    da.SelectCommand.Parameters.AddWithValue("@id", txt_id.Text)

    ' Fill the dataset'
    da.Fill(dset)
    If dset.Tables(0).Rows.Count > 0 Then
        ' Supposing you have a field for the studentname in the first column of the returned
        ' datatable rows(rowindex)(columnindex)
        txtStudentName.Txt = dset.Tables(0).Rows(0)(0).ToString()
        .....
        ' Set the text property of other textboxes for other fields to show'
    Else
        MsgBox("No Record Found")
    End If

在vb.net中获取单值表单数据库

id name

2 个答案: