Hello,
The queries that i create frequently have 7-8 joins to retrieve data. Are these many joins normal in a real database application or is my database design poor? I am curious because if on each request database has to do so much work, then won't it die if few thousands of client connect?
In my opinion it's inevitable in some cases, the key is to have the correct indexes for the queries you're doing. With a deep object graph in ORM, or perhaps one with joined subclasses, it'd be easy to go over the 7-8 joins you talk of. I'm keen to hear what everyone else has to say about it :)
That is a lot of joins. It's hard to say without seeing your schema, but I have seen cases where people have gone nuts making a schema overcomplicated. I remember one application I worked on where every address and phone number in the system was treated as an entity, and queries frequently involved joins of over a dozen tables. You should be careful when making a schema to distinguish between those things you care about individually tracking and everything else, otherwise you can end up with needless complexity.