Simple IP logging script

I just found this:

<?
mysql_connect("localhost","username""pass");
mysql_select_db("dbname");

$ip = $_SERVER['REMOTE_ADDR'];
mysql_query("INSERT INTO IpLogs (Ip) VALUES ('$ip')") or die(mysql_error());
echo '<br>IP logged.';
?>

But now I need to know how to do that if statement to see if the IP is already in the DB:

if ip is in db {
echo “its there”;
} else {
echo “it’s not”;
}