Where can I find tutorials about creating a social network (like db structure, sql query samples eg.) using PHP & MySQL ? I do not need a ready script, I just want to learn how to do it..
Pretty hard to do one from scratch.
My opinion is that you should really break it into smaller pieces. Like, how to make a good log-in. How to keep the users into a database. What info do you need about them, what kind of social network should it be? Things like that. After you will put many many pieces together you will see the image from the puzzle and then you will wonder, what frameworks should I use to make my life easier? How will the network look like?
If you are just starting with php I don't recommend you starting with this. Learn to lurk before you leap.