We're designing a database in which I need to consider some FK(foreign key) constraints. But it is not limited to formal structuring and normalization. We go for it only if it provides any performance or scalability benefits.I've been going thru some interesting articles and googling for practical benifits, here're some links:http://www.mssqltips.com/tip.asp?tip=1296I wanted to know more about the benefits of FK (apart from the formal structuring and the famous cascaded deleteupdate) FK are not 'indexed' by default so what are the considerations while indexing an FK? How to handle nullable fields which are mapped as foreign key - is this allowed? Apart from indexing, does this help in optimizing query-execution plans in SQL-Server? I know there's more but I'd prefer experts speaking on this. Please guide me.