PHP MySQL generating unique random number

Question

I don't understand why my code isn't working. The connection works and everything else however when I try to generate a unique random number and check from the MySQL if the number is there it still prints out a random number but it's not UNIQUE. Could anyone help me thx? Here's my code:

$num = rand(1,5);
$sel_query  = "SELECT *  FROM  test"; 
$result2 =  $con->query($sel_query);

$i = 1;
for (;$i<2; $i++)
{
    while($row = mysqli_fetch_array($result2))
    {
        if ($row['id'] == $num) 
        {
             $num = rand(1,5);
             $i = 0; 

        }
    }
}

what is the column of the rand number in the DB you can simply do a search for it instead of looping through... — David Nguyen, Mar 12 '13 at 04:14
This might help you: http://stackoverflow.com/questions/8834493/how-generate-unique-random-number-in-php — Subedi Kishor, Mar 12 '13 at 04:19
What are you trying to accomplish? Just fetch a random row from a table? What do mean by *...but it's not UNIQUE*? — peterm, Mar 12 '13 at 04:29

Jodes · Accepted Answer · 2013-03-12T05:40:56.523

2

This should work:

$is_unique = false;
$num = false;
while (!$is_unique){
    $num = rand(1,5);
    $sel_query  = "SELECT id from test where id = " . $num; 
    $result2 =  $con->query($sel_query) or die($conn->error);
    if (!mysqli_fetch_array($result2)){
        $is_unique = true;
    }
}
echo "Unique number is " . $num;

But if there aren't any more possible unique numbers, it will loop forever.

edited Mar 12 '13 at 05:40

answered Mar 12 '13 at 04:44

Jodes

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i got an error: Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in – user2138160 Mar 12 '13 at 05:14
There's some sort of error then. I've edited it, try it now, it should output the error. – Jodes Mar 12 '13 at 05:41

score 1 · Answer 2 · answered Jun 17 '15 at 20:22

I know this is a bit old, but I found this question after needing a similar answer. I've taken Jodes's answer and updated it slightly, so that it won't run forever, is a function that returns the number, and accepts a mysqli connection as $mysqli:

function getUniqueNumber($mysqli)
{
    $is_unique = false;
    $num = false;
    $times_run = 0;
    while (!$is_unique)
    {
        if($times_run > 10)
        {
            echo "Run too many times, dying.";
            die();
        }
        $num = rand(1,5);
        $sel_query  = "SELECT id from test where id = " . $num; 
        $result2 =  $mysqli->query($sel_query) or die($mysqli->error);
        if (!mysqli_fetch_array($result2))
        {
            $is_unique = true;
        }
        $times_run++;
    }
    return $num;
}

PHP MySQL generating unique random number

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