Generate unique random numbers to be stored in database

Question

Below is my code to check if the generated random number is available in the database. If the $smsCode is already in the database, then generate a new random number. But it is not working as expected.

$smsCode = 7552;
        $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'";
        while($conn->query($query) === TRUE){
            $smsCode = rand(1000,9999);
            $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'";
            $conn->query($query);
        }
$sql = "INSERT INTO appointment(number) VALUES('$smsCode');

$smsCode = 7552 is already in the database but it keeps storing 7552 into the database instead of generating a new number to be stored in the database.

Manikiran · Accepted Answer · 2015-10-18 06:05:16Z

2

<?php
$sms_code=rand(1000,9999);
$cond=True;
while($cond){
    $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'";
    $result = $conn->query($query);
    if(mysql_num_rows($result)>0)
    {
        $sms_code=rand(1000,9999);
    }
    else
    {
        $cond=False;
    }
}
$sql = "INSERT INTO appointment(number) VALUES('$smsCode')";
?>

answered Oct 18, 2015 at 6:05

Manikiran

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1 Comment

mickmackusa Over a year ago

This is NOT "race condition" safe.

bish · Accepted Answer · 2015-10-18 07:00:50Z

1

If the result of your first query returns a valid result it doesn't return true. The query() function only returns false if it fails, see PHP manual. So the condition of your while-loop where you make a comparison to the boolean true (cause of strict type comparions with three =) will never be true and so no new value is assigned to $smsCode.

Try something like this

$smsCode = 7552;

while(true) {

    $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'";
    if($conn->query($query) === false) {
      $sql = "INSERT INTO appointment(number) VALUES('$smsCode')";
      break;
    } else {
      $smsCode = rand(1000,9999);
    }
}

This should generate a new code every time you don't have row in your database with that code.

edited Oct 18, 2015 at 7:00

answered Oct 18, 2015 at 6:06

bish

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4 Comments

Manikiran Over a year ago

You need to add " to the end of $sql

bish Over a year ago

Ops didn't copied the whole query :O Thanks

Manikiran Over a year ago

You need to place it before ;, but anyways, its more efficient than my code :)

mickmackusa Over a year ago

A do { ... } while () would be more sensible syntax. BUT this approach is NOT "race condition" safe.

Shaymol Bapary · Accepted Answer · 2015-10-18 07:10:28Z

0

you can try this

$date = date_create();
$smsCode = date_timestamp_get($date);

each time it will give you an unique random numbers

answered Oct 18, 2015 at 7:10

Shaymol Bapary

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