Trying to check if username already exists in MySQL database using PHP

Question

I\'ve looked at the many other posts that were similar to my issue and implemented their solutions (as far as I can tell) as exactly as I could. However, every time I execut

Answer 1

Here's one that i wrote:

$error = false;
$sql= "SELECT username FROM users WHERE username = '$username'";
$checkSQL = mysqli_query($db, $checkSQL);

if(mysqli_num_rows($checkSQL) != 0) {
   $error = true;
   echo '<span class="error">Username taken.</span>';
}

Works like a charm!

Answer 2

change your query to like.

$username = mysql_real_escape_string($username); // escape string before passing it to query.
$query = mysql_query("SELECT username FROM Users WHERE username='".$username."'");

---

However, MySQL is deprecated. You should instead use MySQLi or PDO

Answer 3

TRY THIS ONE

 mysql_connect('localhost','dbuser','dbpass');

$query = "SELECT username FROM Users WHERE username='".$username."'";
mysql_select_db('dbname');

    $result=mysql_query($query);

   if (mysql_num_rows($query) != 0)
   {
     echo "Username already exists";
    }

    else
   {
     ...
    }

Answer 4

Try this:

$query = mysql_query("SELECT username FROM Users WHERE username='$username' ")

Don't add $con to mysql_query() function.

Disclaimer: using the username variable in the string passed to mysql_query, as shown above, is a trivial SQL injection attack vector in so far the username depends on parameters of the Web request (query string, headers, request body, etc), or otherwise parameters a malicious entity may control.

Answer 5

PHP 7 improved query.........

$sql = mysqli_query($conn, "SELECT * from users WHERE user_uid = '$uid'"); if (mysqli_num_rows($sql) > 0) { echo 'Username taken.'; }

Answer 6

Everything is fine, just one mistake is there. Change this:

$query = mysql_query("SELECT username FROM Users WHERE username=$username", $con);
$query = mysql_query("SELECT Count(*) FROM Users WHERE username=$username, $con");

if (mysql_num_rows($query) != 0)
{
    echo "Username already exists";
}
else
{
  ...
}

SELECT * will not work, use with SELECT COUNT(*).