duplicated data display

Hi all. i have the following function below,which use to retrieve the order detail from 2 table which are order detail and product. i have many duplicated order id in order detail, and each order id has a unique product id which link to product to display the product information. however when i run the following function below . its duplicated each product info and dsplay in the combo box. May i know whats wrong with my code?

Public Sub ProductShow()

Dim myReader As SqlCeDataReader
Dim mySqlCommand As SqlCeCommand
Dim myCommandBehavior As New CommandBehavior
Try
connLocal.Open()
mySqlCommand = New SqlCeCommand
mySqlCommand = connLocal.CreateCommand
mySqlCommand.CommandText = "SELECT * FROM Product P,orders O,orderdetail OD WHERE OD.O_Id='" & [Global].O_Id & "' AND P.P_Id=OD.P_Id "
myCommandBehavior = CommandBehavior.CloseConnection
myReader = mySqlCommand.ExecuteReader(myCommandBehavior)
While (myReader.Read())
cboProductPurchased.Items.Add(myReader("P_Name").ToString())
End While
myReader.Close()
Catch ex As Exception
MsgBox(ex.ToString)
Finally
connLocal.Close()
End Try

End Sub

Can you please provide sample data also?

Thanks,

Laxmi Narsimha Rao ORUGANTI, MSFT, SQL Mobile, Microsoft Corporation