Tariq,
Pretty vague question. You can create joins in an ABAP program, or while creating a view, or when creating a SAP query of one type or another. Some people download tables and then join them using desktop software. If you can elaborate your question I may be able to give you a better answer.
I recently joined two wooden tables at a picnic. I used 24 gauge galvanized wire combined with duct tape, so I guess you couldn't really call that an 'inner join'.
Best Regards,
DB49