Question

I’m working on designing a “friend” system for my site. I have a USERS table in my database and two fields in that table called “friendrequestssent” and “friendrequestsreceived”.

When a user sends a friend request to another user, it stores his USERID into the other person’s “friendrequestsreceived” field and the other person’s USERID into his “friendrequestssent” field, both with a trailing comma (ie: 12345,).

I need to check to see if a request already exists in order to prevent duplicate requests, and so far I’ve tried this:

$sql = "SELECT * FROM users WHERE userid = $userid AND $profileid IN (friendrequestssent);";
    $sent = mysql_num_rows(mysql_query($sql));
    $sql = "SELECT * FROM users WHERE userid = $profileid AND $userid IN (friendrequestsreceived);";
    $received = mysql_num_rows(mysql_query($sql));
    if(($sent > 0) && ($received > 0)) {
//do stuff here
}

This worked great at first, but when multiple comma-separated values exist in the field (ie: 12345,12346,) , the IN statement no longer finds the value and the number of rows remains zero.

As far as I can tell, I cannot see why the IN statement in the MySQL query won’t see the value.

On the other hand, I’m sure there is a far better way to do this anyway. I’m just not sure how yet. Please advise.

Answer 1

Your design is OK, but it will be better if you let me redesign this for you:

First leave your table users as it is, then do a new table with 3 fields:

• An autoincrement field as your index (if you want it, or just skip this column).
• A field where you store a friend that is requesting a friendship and lets call: friend_request.
• A field where you store the friend that is receiving the friendship request, and lets call ir: friend_receive_request.

You should add the propper foreign key indexes and be aware that you could have duplicate requests by storing the same friendship in different columns. I could clear this more if you have questions.