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up vote 2 down vote favorite

Why doesn't this code work?

It creates a random number, if it exists in database then it generates a new one until it can insert into the unique key, if not then it inserts straight away into database.

$id;
    do {
    $id = mt_rand(1, 10);
    "SELECT count(*) FROM accounts WHERE id = '$id'";
    } while (count != 0);

    $sql = "INSERT INTO accounts (id, username, email, password, sex)
    VALUES ('$id', '$username', '$email', '$password', '$sex')";

The reason the mt_rand is low for testing purposes.

share|improve this question
No it is not, the purpose of my script is purposefull enough to need it working. – phpabuse Apr 2 '11 at 3:44
Check my solution then :-? and tell me if it works as intended. – Khez Apr 2 '11 at 3:50

4 Answers

up vote 2 down vote accepted

That is because, you are not really firing a mySQL query. You just have the query string as such. You must pass the string the mysql_query(..). Retrieve the resource, and then check out the final number of rows.

Method #1: (modifying your code)

$id;$count;
do {
    $id = mt_rand(1, 10);
    $res = mysql_query("SELECT count(*) as c FROM accounts WHERE id = '$id'");
    $row = mysql_fetch_array($res);
    $count = $row['c'];
} while ($count != 0);

$sql = "INSERT INTO accounts ...";
//..

Method #2:

  • Modify your MySQL table, use an auto_increment. Create a table this way
  • create table myTABLE (
    id integer aut_increment,
    username varchar(128),
    email varchar(128),
    ..
    primary key(id)
);
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up vote 1 down vote

Why are you going about generating an ID using this method? Why wouldn't you just use an auto-incrementing ID?

CREATE TABLE accounts (
     id INT NOT NULL AUTO_INCREMENT,
)

Generating an ID using using mt_rand doesn't make a whole lot of sense and will be incredibly expensive with the more accounts that you get.

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3  
Personally, I like having the occasional O(n^Infinity) method though... – cwallenpoole Apr 2 '11 at 3:46
up vote 0 down vote

Erm... there seems to be some mild issues in that code:

$id;
do {
    $id = mt_rand(1, 10);
    $c=mysql_query('SELECT id FROM accounts WHERE id = '.$id.' LIMIT 1;');
}while(mysql_num_rows($c)!=0);

P.S. You should consider looking into: uniqid in the PHP manual and auto-incrementing an sql field

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this query always returns 1 row, the limit and the mysql_num_rows are pointless – Paul Creasey Apr 2 '11 at 3:54
unless... it fails o.o – Khez Apr 2 '11 at 3:56
up vote 0 down vote

Several things

  1. It is not using mysql_query.
  2. It is not fetching the result of the query (which doesn't exist)
  3. count is a built in PHP method, not a number.
  4. You should not be having that many round trips to the database (it is a very bad idea to generate a random identifier that way)
share|improve this answer
So what would you do? – phpabuse Apr 2 '11 at 3:47

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