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
– David Nguyen, Commented Mar 12, 2013 at 4:14
This might help you: stackoverflow.com/questions/8834493/… — Subedi Kishor
– Subedi Kishor, Commented Mar 12, 2013 at 4:19
What are you trying to accomplish? Just fetch a random row from a table? What do mean by ...but it's not UNIQUE? — peterm
– peterm, Commented Mar 12, 2013 at 4:29

Jayy · Accepted Answer · 2013-03-12 05:40:56Z

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, 2013 at 5:40

answered Mar 12, 2013 at 4:44

Jayy

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2 Comments

user2138160 Over a year ago

i got an error: Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in

Jayy Over a year ago

There's some sort of error then. I've edited it, try it now, it should output the error.

Dwebtron · Accepted Answer · 2015-06-17 20:22:11Z

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;
}

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