檢查用戶名是否已被使用

Question

如何檢查用戶名是否已經被數據庫佔用？ 我曾嘗試這個代碼，但沒有奏效

$usernamecheck=mysql_query("SELECT userName FROM websiteusers WHERE userName='$_POST['username']'"); 

Answer 1

你可以試試這個：

$user = $_POST['username']; 
    $usernamecheck=mysql_query("SELECT `userName` FROM `websiteusers` 
          WHERE userName='$user'", $dbcon); 
if(mysql_num_rows($usernamecheck)>=1){ 
    echo $user." is already taken"; 
}else{ 
    echo $user."is available"; 
} 

Answer 2

$usernamecheck=mysql_query("SELECT userName FROM websiteusers WHERE userName='".$_POST['username']."'");