You need to do a select query..

select * from table_name where column1="value1" and column2="value2" ...

The answers to these sort of questions are in php/mysql tutorials all over the internet.

select * from table_name


this lis all the values in table .

g0 to w3schools.com this is very usefull site for bignner

use this command

$res=mysql_query("select * from table name where value1= $_post['value1']");

if (mysql_num_rows($res)>0)

{
$ans="value already exist";

}
else
{
$ans="....insert command...";
}

thanks dude! So then it would look like this?

PHP Syntax (Toggle Plain Text)

$res=mysql_query("SELECT * FROM registered_members=$_POST['Username']");
if (mysql_num_rows($res)>0)
{
echo "Username is already taken!";
}
else
{

$res=mysql_query("SELECT * FROM registered_members=$_POST['Username']"); if (mysql_num_rows($res)>0) { echo "Username is already taken!"; } else {

ok then i get this error:
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource.