How to check if entry is already in db?

AJPayne

Well I have a form, and I want to check whether a specific filed is already in the db or not. If it is not, then it adds it to the db. If it is already in the db, then redirect to another page and tell the user that it is already in the db...

How do I do that in PHP?

Thanks

tsinka

Hi,

let's say you want to check if a given user already exists then do something like:

<?PHP
$user = $_POST['username'];

$res = mysql_query("SELECT COUNT(*) AS cnt FROM thetable WHERE user='"
           .mysql_escape_string($user)
           ."'");
$row = mysql_fetch_array($res);
$cnt = $row['cnt'];
if ($cnt>0) {
  // user already exists
} else {
  // user doesn't exist
} 
?>

Thomas

Roger_Ramjet

    // Check for existing user with the new id
    $sql = "SELECT COUNT(*) FROM user WHERE userid = '$_POST[newid]'";
    $result = mysql_query($sql);
    if (mysql_result($result,0,0)>0) {
    // insert your redirect here
        exit;
    }

Try header("Location: http://www.example.com/"); for a redirect

AJPayne

Originally posted by tsinka
Hi,

let's say you want to check if a given user already exists then do something like:

<?PHP
$user = $_POST['username'];

$res = mysql_query("SELECT COUNT(*) AS cnt FROM thetable WHERE user='"
           .mysql_escape_string($user)
           ."'");
$row = mysql_fetch_array($res);
$cnt = $row['cnt'];
if ($cnt>0) {
  // user already exists
} else {
  // user doesn't exist
} 
?>

Thomas [/B]

I did this

		$url = $_POST['company_url']; 

	$res = mysql_query("SELECT COUNT(*) AS cnt FROM hosts WHERE company_url='" 
       		.mysql_escape_string($url) 
       		."'"); 
	$row = mysql_fetch_array($res); 
	$cnt = $row['cnt']; 

	if ($cnt>0)
	{ 
		print 'Host already exists.';
		exit;
	} 

	else
	{
		mysql_query($query,$conn) or die("SQL error: ".mysql_error());
		mysql_close($conn);
		header("Location: tu.php");
		exit;
	}

But it doesn't work. It fails the test whether the url is already in the db or not, and adds it anyway...

Any ideas?

Thanks

tsinka

Ok,

add a

echo "The url is: ".$url."<br>\n";

in front of the mysql_query line. Then execute that query manually through e.g. phpMyAdmin and check the returned data.
Thomas