Visual Basic.NET - Dos DataGridView relacionados

Public Class Form1

    Private db As db_camionetasEntities

    Private db2 As db_camionetasEntities

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        db = New db_camionetasEntities

        db.tbl_camionetas.Load()

        TblcamionetasBindingSource.DataSource = db.tbl_camionetas.Local

        db2 = New db_camionetasEntities

        db2.tbl_asignacion.Load()

        TblasignacionBindingSource.DataSource = db2.tbl_asignacion.Local

    End Sub

end class

Private db As db_camionetasEntities

Private db2 As db_camionetasEntities

Public sub Lectura_Datos

    Using cn As SqlConnection = 'aqui debe de colocar la ruta de tu base de datos

        Try

            cn.Open()

            Dim StrSql As String = " SELECT * FROM TABLA_1 INNER JOIN TABLA_2 ON TABLA_1.COLUNA_CODIGO = TABLA_2.COLUNA_CODIGO"

            Dim cmd As  New SqlCommand(StrSql, cn)

            Dim da As New SqlDataAdapter(cmd)

    Dim dt As New DataTable

            da.Fill(dt)

         Datagridview.datasource = dt

        Catch ex As Exception

            MsgBox(ex.Message, MsgBoxStyle.Critical, "ERRO ")

        Finally

            cn.Close()

        End Try

    End Using

    Return dt

End Function

SELECT * FROM TABLA_1

SELECT * FROM TABLA_2