> /home/user/user1/user1.db [User1 will have table to hold contacts list] > /home/user/user2/user2.db [User2 will have table to hold contacts list] > . > . > . > /home/user/userN/userN.db [UserN will have table to hold contacts list]
This would imply that you are writing an application where each user has their own file structure (like a word processor would, for example). i.e. the user logs in and runs the app, accessing their own files. If this is the case, then yes, what you are suggesting is correct since the various contact lists are isolated entities. If, however, the users share the app and there is one data file, then the normalization argument kicks in. In this case you would have two, or possibly three tables. The first would contain all your user's details (including, if appropriate, security information to allow the application to authenticate them) One column would be a unique ID number, known as the primary key. A second table would contain the contact details. One column of that would be the id of the "owning" user (known as a foreign key). So when your application wants to list a user's contacts it searches for only those contacts that are "owned" by the user (i.e. the contacts whose foreign key is the user's primary key). It gets better! If, say, two users have the same contact then there will be two entries in the contacts table and therefore two entries to keep up to date. Let's say you want to be able to share contacts. Now what you do is to have a primary key on both the users and contacts tables (I always have a primary key on every table anyway) and a third table which contains two columns of foreign keys, one for the user and one for the contact. Now, each user can have multiple contacts and each contact can have multiple users. In this case, I would probably include information in the relationships table to control which user can edit the contact, but the point is if, say, I had you in my contacts list and I shared that contact with my wife, if your details changed and I edited them, my wife's version would change too. That, in a nutshell, is normalization. I hope that helps, but like I said at the start, it depends how you see your app working. Your original question implied that you would have 1 file and many tables in it (1 for each user) which would be wrong (well, inefficient!) I hope that helps. -- Paul ----------------------------------------------------------------------------- To unsubscribe, send email to [EMAIL PROTECTED] -----------------------------------------------------------------------------
