How to perform arithmetic operations on the database records using vb.net

Hello !
These are my two tables which are named Table1 and Table2 ( I know they aren't good names but I created them hastily)
In table1 , I have following fields

Code:

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[Train_Number], [Train_Name],[Starting_point],[Destination],[Fare]

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In table2 , I have

Code:

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[P_Name],[Age],[Phone],[Train_Name],[Tnumber]

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I want have created a ticket cancellation system in which the user enters his [Tnumber] and [Phone]and his ticket gets cancelled but I want vb to display the confirmation receipt to the user after the ticket has been cancelled . The confirmation receipt should also contain the refundable money which is 20% of the respective train of the passenger .
I think I would have to join these two tables to fetch the record [Fare] from Table1 as both the information which users enters are in Table2 . The Table2 also contains the name of the Train so , I think we can join both the tables using this field .
The problem is that I don't know how should I do this . I have searched google also but have not found anything . Please help me . This is my cancellation form code .

Code:

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Imports System.Data.OleDb
Public Class Form5
    Public Connstring As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source = C:\Users\AMEN\Documents\Railway.accdb"
    Public Conn As New OleDbConnection

    Private Sub Form5_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Conn.ConnectionString = Connstring
        If Conn.State = ConnectionState.Closed Then
            Conn.Open()
        End If

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim emptyTextBoxes =
  From txt In Me.Controls.OfType(Of TextBox)()
  Where txt.Text.Length = 0
  Select txt.Name
        If emptyTextBoxes.Any Then
            MsgBox("Please fill the empty feilds ")

 Else

            Dim okToDelete As MsgBoxResult = MsgBox("Are you sure you want to cancel your ticket?", MsgBoxStyle.YesNo)
            If okToDelete = MsgBoxResult.Yes Then
                Dim str As String
                str = "Delete from Table2 Where Phone = '" & TextBox1.Text & "' and Tnumber= " & TextBox2.Text
                Dim cmd As OleDbCommand = New OleDbCommand(str, Conn)
                Try
                    cmd.ExecuteNonQuery()
                    cmd.Dispose()
                    Conn.Close()

                    MsgBox("Your Ticket Cancelled Sucessfully ! ")
                Catch ex As Exception
                    MsgBox(ex.Message)
                End Try
            ElseIf okToDelete = MsgBoxResult.No Then
            End If



            Form3.Show()
            Me.Close()

        End If
    End Sub

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Yea, the way your tables are setup, you would need a JOIN. You could reevaluate the table structure though and not need it. As you have it, it looks like Table1 has information about a specific train ride including how much it cost. If you where to move the cost of the trip to Table2, then you have a bit more flexibility by allowing different passengers to pay different amounts (kid rate, senior rates, discounts, ect.) In doing so, you would no long need a join, since all of the information is in a single table. Insofar as doing math in SQL you should be able to do something like this...

Code:

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SELECT (fare * .2) FROM table1 WHERE <someField> = <someValue>

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Thank you ! Can i also display this value in the msgBox?

Sure, you can show anything you want in a message box just as long as it can be displayed as a string.