To specify a little bit further, with option 1, the user can still open the table (with Excel for example) and view the content. You will need option 2 or a different backend (like SQL Server) to prevent a client to view the content of a table.
>1) Have all data access go through a DLL. The user won't have direct access to the data.
>2) Use an encryption tool. Look at
www.hallogram.com for one.