ช่วยให้ความรู้ผมทีครับ ทำไมcode1ถึงไม่error แต่code2ถึงerror ทั้งที่เป็น select เหมือนกัน

        Dim connection As String = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True"
        Dim conn As New SqlConnection(connection)
        conn.Open()
        Dim comm As String = "INSERT INTO GUES(GUES_NAME,GNDR,NATN,IDEN,E_MAIL,ADDR,TELP_NO)"
        comm &= "VALUES('" & TextBox1.Text & "',"
        comm &= "'" & TextBox2.Text & "',"
        comm &= "'" & TextBox3.Text & "',"
        comm &= "'" & TextBox4.Text & "',"
        comm &= "'" & TextBox5.Text & "',"
        comm &= "'" & TextBox6.Text & "',"
        comm &= "'" & TextBox7.Text & "')"
        Dim command As New SqlCommand(comm, conn)
        command.ExecuteNonQuery()

        comm = ("select top 1 GUES_ID from GUES ")
        command = New SqlCommand(comm, conn)
        Dim reader As SqlDataReader = command.ExecuteReader()
        reader.Read()
        Dim Personalid As Integer = reader("GUES_ID")
        reader.Close()

        comm = "INSERT INTO RESV(GUES_ID,ROOM_ID,DATE_FROM,DATE_TO,RESV_STTS,DATE_RESV)"
        comm &= "VALUES('" & Personalid & "',"
        comm &= "'" & lblSeleceRoom.Text & "',"
        comm &= "Convert(DateTime, '" & lblSeleceDate.Text & "', 103),"
        comm &= "Convert(DateTime, '" & lblSeleceDate1.Text & "', 103),"
        comm &= "'A',"
        comm &= "'" & DateNow & "')"
        Dim acommand As New SqlCommand(comm, conn)
        acommand.ExecuteNonQuery()
        conn.Close()
    End Sub
End Class

Dim connection As String = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True"
        Dim conn As New SqlConnection(connection)
        conn.Open()
        Dim comm As String = "INSERT INTO GUES(GUES_NAME,GNDR,NATN,IDEN,E_MAIL,ADDR,TELP_NO)"
        comm &= "VALUES('" & TextBox1.Text & "',"
        comm &= "'" & TextBox2.Text & "',"
        comm &= "'" & TextBox3.Text & "',"
        comm &= "'" & TextBox4.Text & "',"
        comm &= "'" & TextBox5.Text & "',"
        comm &= "'" & TextBox6.Text & "',"
        comm &= "'" & TextBox7.Text & "')"
        Dim command As New SqlCommand(comm, conn)
        command.ExecuteNonQuery()

        comm = ("SELECT MAX(GUES_ID) AS MaxGUES_ID FROM GUES")
        command = New SqlCommand(comm, conn)
        Dim reader As SqlDataReader = command.ExecuteReader()
        reader.Read()
        Dim Personalid As Integer = reader("GUES_ID")
        reader.Close()

        comm = "INSERT INTO RESV(GUES_ID,ROOM_ID,DATE_FROM,DATE_TO,RESV_STTS,DATE_RESV)"
        comm &= "VALUES('" & Personalid & "',"
        comm &= "'" & lblSeleceRoom.Text & "',"
        comm &= "Convert(DateTime, '" & lblSeleceDate.Text & "', 103),"
        comm &= "Convert(DateTime, '" & lblSeleceDate1.Text & "', 103),"
        comm &= "'A',"
        comm &= "'" & DateNow & "')"
        Dim acommand As New SqlCommand(comm, conn)
        acommand.ExecuteNonQuery()
        conn.Close()
    End Sub
End Class