I need make a db to register 1.000 users, and each user will have +- 70 informations. What is faster, make 1.000 tables with 2 or 3 fields, 70 entries and the user name in the table's name, or a table with 1.000 entries and 70 fields, with a field to store the user's name???
You can stick several elements together in longer strings if you like, to be interpreted by the PHP (or whatever) code in the script. Explode is your friend.
Generally, more databases is worse than more tables. More tables is worse than more fields. More fields is worse than more records. Better than more records is records with information that you are likely to gather at the same time (like friend 1, friend 2, friend 3, ...) in one field (like "friend 1:friend 2:friend 3:..." all in one). But don't go overboard! Username should definitely be one field, and user ID ought to be there as a primary key too. Just use your discretion together with these tips for a database with an efficient structure.
Fire Boar, to put a lot of things in the same field is probably not a good idea. The database structure should be adapt to the way it will be used. The example with "friend 1, friend 2, friend 3, ..." in one field I totally disagree to. This is probably a case where you want to create a new table that holds the relation between the two users. Two fields, user and friend which both holds the a user's key value and where both is part of the primary key. In this way it's very easy to handle the data and make joins to other tables.
MySQL is built with heavily optimized code for handling databases efficiently - just put all the data how it should be logically, like a table with all of the users and their information in separated fields, use commands to get just the data you need, and you should be fine. (If you need to look up user #2's favorite color, don't do "SELECT * FROM users WHERE id=2", but "SELECT color FROM users WHERE id=2" [it's been a while since I've used sql, so that command might not be exactly right but you see where I'm going with it])
Thanks for all!!!
It was very useful, and forgive my bad, bad english... I will do like AgentMe says, and when i finish my project i will try make some "experiments".