如果用户也使用php选择了用户名，请在MySQL表列中输入用户名

Question

I would like to set up a voting system to buddy up a fair few people in a table if they select each other. An example table would be

---------------------
User | vote | Buddy |
---------------------
A    |C     |no     |
B    |C     |C      |
C    |B     |B      |
D    |G     |no     |
E    |no    |no     |
F    |G     |no     |
G    |A     |no     |
---------------------

The votes are cast by a radio button form, where users have a choice of anyone but themselves. These choices then update the vote column with the username of the person they have voted for. In this instance user E has not voted, and so has the default 'no'. I have built up to this point.

Next, I would like there to be a comparison of the user and vote column. If one user has voted for another, and they in turn have voted for them, I would like their username added to the users buddy column. In this instance, B would like to buddy with C and C would like to buddy with B, so there is a match and each others users names have been added to the buddy column. Although a couple of people voted for G, G voted for A, and so no further additions to the buddy column need to be added in this instance, so remain at the deafult 'no'.

I've guessed that a way to do it may be to cycle through the user column, select which one they have voted for and compare that choice with the choice of the user they voted for. However, putting this into code has proven very difficult, and so far I've only managed this code below. I tried to narrow it down to only users who have been voted for, before cycling through to save time. I'm not that keen on the 2 selections, I guess that one can go, and I know it won't be ideal to SELECT * for this basic function, but it's there whilst I work on it while the table is in trial mode in case I think of another column that may help.

$sql = <<<SQL
SELECT *
FROM `table` 
SQL;

if(!$result = $db->query($sql)) {
    die('There was an error running the query [' . $db->error . ']');
}
if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        $vote = $row['vote'];


        $sql2 = <<<SQL
                SELECT *
                FROM `players`
                WHERE user = '$vote';
                SQL;

        if(!$res = $db->query($sql2)) {
            die('There was an error running the query [' . $db->error . ']');
        }    

        if ($res->num_rows > 0) {
            while($line = $res->fetch_assoc()) {
                $user = $line['user'];
                echo $name;
            }
        }
    }
}

Any ideas, answers or tutorials that may help will be much appreciated - let me know if you need any more info. Thanks, Toastie

Answer 1

You would just do this with an update :

update example e join
       example e2
       on e.user = e2.vote and e2.user = e.vote
    set e.buddy = e.vote;