How to check if a value already exists to avoid duplicates?

Question

I\'ve got a table of URLs and I don\'t want any duplicate URLs. How do I check to see if a given URL is already in the table using PHP/MySQL?

Answer 1

$url = "http://www.scroogle.com";

$query  = "SELECT `id` FROM `urls` WHERE  `url` = '$url' ";
$resultdb = mysql_query($query) or die(mysql_error());   
list($idtemp) = mysql_fetch_array($resultdb) ;

if(empty($idtemp)) // if $idtemp is empty the url doesn't exist and we go ahead and insert it into the db.
{ 
   mysql_query("INSERT INTO urls (`url` ) VALUES('$url') ") or die (mysql_error());
}else{
   //do something else if the url already exists in the DB
}