1. I dont know about your database design. But it would better if you added a product code.
2. You can check existing product name before insert in your query/procedure.
2.1. You can check in IF condition with To Upper/ to Lower the both side.
2.2. You can check in IF condition with remove the space and to upper/to lower the both side( I am not talking to remove space for insert, I mean you can use replace method in if condition for checking purpose).
3. In product table you can set unique key type the product name.
For query help you can follow this one
http://stackoverflow.com/questions/17442901/how-to-avoid-duplicate-values-for-insert-in-sql[
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Thanks.