We are trying to display a SAP table content in SharePoint 2010.
What are the different ways to achieve this?
One way we thought to do is with SAP .NET Connector.
However which method will be best ?
You can use the SAP .Net Connector with VS 2010 by building wrapper classes around it in VS2003 and then consuming those, but maintenance is a ... challenge.
There's a new version of the SAP <-> .Net connectivity middleware available, but I have no experience with it. Information is available in the SAP forums - I would point you to it, but I don't work at the company where I used SAP with .Net any longer so I don't have access to the forums. I would investigate that before attempting anything with the .Net connector.
Speaking from memory, depending on which SAP Applications you have there are web services accessible for many SAP activities - again I have no experience with these, but there are sections of the forums dedicated to them as well. In either scenario if you have access to an ABAP programmer and the functionality you need is not exposed in the built-in APIs they can be exposed as remote function calls by custom code.
One thing I would not do is to update the SAP database directly. There are a lot of interconnected tables in the SAP system and updates are synchronized across them by the internal SAP code. If you make updates to a table directly you are bound to miss some of the correlated updates to other tables that the system makes and cause yourself no end of trouble. If you're updating information in SAP, stick to the exposed APIs or write your own in ABAP that rely on the internal functions. If you're just reading data you would probably be OK reading directly from the database, although in my experience it's sometimes very difficult to figure out which tables the information is stored in, and some of it is stored in "transparent tables" that look like database tables to the SAP system but have no on-disk representation.