How to prevent multiple entries to db

[mmarif4u]

Hi everybody,,,
I am facing problem,
Problem is that i have a user with ic already have in my database.
But my query enter another data to db when i try to enter that ic
again.i want that only one ic exist in db.i make query but t only checks the
format like 1234 or 5462313 not 123aa and 123333-12-1234
I want to check the format like 123456-12-1234..
My query is:

// Check for existing user with the ic number
    $sql = "SELECT COUNT(*) FROM loguser WHERE icnumber = $ic ";
    $result = mysql_query($sql);
    if (!$result) {    
        error('A database error occurred in processing your '.
             'submission.\\nIf this error persists, please '.
              'contact [e-mail].');
    }
 
 
    if (mysql_result($result,0,0)>0)  {
        error('A user already exists with your chosen IC Number.\\n'.
              'Please try your own IC Number.');
    }
    if (preg_match('#^[0-9]{6}-[0-9]{2}-[0-9]{4}$#', $ic))
    {}else{      
    error('IC Number format is not Valid.\\n'.
              'Please try again.');
       }
 
 

please any one has idea about it,,
i think the error is here thats why it didnot check the format entered.

if (mysql_result($result,0,0)>0)  {
 

Thanks in advance

[mmarif4u]

Problem Solved