[display the cars in an ordered list based on the average of their scores]

I have a database called cars
it contains
car_id
carname

There is another database that contains the votes submitted and is structured the following way
voteid
car_id
vote_value

TRYING TO ACCOMPLISH: output name of cars in increasing order of their average score

In the votes table, there can exist several entries for one specific car.

any idea?

[attachment deleted by admin]

[inversing a selection when joining tables]

AWESOME IT WORKED
thanks shoz

lol hey I used the minimal knowledge to try and get it working :)

[inversing a selection when joining tables]

table 1 (users)
userid
username

table 2(payments)
paymentid
userid

I need two things
USERIDS of those who PAID. This works:
SELECT u.userid FROM users u JOIN payments ON u.userid = payments.userid;

USERIDS of those who haven't paid. This is my problem
I tried something along the lines of: but no luck
SELECT u.userid FROM users u LEFT JOIN payments ON u.userid = payments.userid LIMIT 99999 OFFSET ("SELECT ( (SELECT COUNT(*) FROM users)-(SELECT COUNT(*) FROM payments) ));
but no luck

anyone have an idea?

[how to structure database to handle user's friends]

What would be the best way to structure a database so that users can add friends.

Right now i have a simple user table which includes
userid
username
password
emai

thanks

edit:
ok more info:
let's say the following user
1
boonamera

wants to add as a friend
2
booya

how would you record this relationship?
I'm asking what field would you put in the friends table if that's how you suggest doing it.

[redirecting to different page after having sent data]

thanks guys

I got 2 versions working: with the meta and with the include

I couldn't use header as i had outputted preivously.

I think the include method should do the trick but the only problem with it is that I would like the address to show http://domain.com/error
anyways of doing that?

Otherwise ill stick with the meta,

thx

[redirecting to different page after having sent data]

basically i'm trying to do something like this:

index.php has:

if($category == 0)
{
          // GO to error.php
}

how would i go about making the page refresh to error.php?
So if i understood correctly i can't used  header because I have data above it.
Then i can't use meta because that needs to be in the header.

What's left?

[multiple variable post]

edit: mybad will try to make myself clearer, first I'll reevaluate what i want to accomplish