Question

我的注册表单中包含以下代码，以防止创建多个用户名：

connect_db();
    $check = mysql_query("SELECT username FROM school_users WHERE username = '$username'") or die(mysql_error());
    $check2 = mysql_num_rows($check);

if ($check2 != 0) {
    respond("error", "Sorry, the username ".$_POST['username']." is already in use. Please choose a different username.");}

但是，我也想在同一声明中检查电子邮件：

    connect_db();
        $check = mysql_query("SELECT username, email FROM school_users WHERE username = '$username' or email = '$email'") or die(mysql_error());
        $check2 = mysql_num_rows($check);

    if ($check2 != 0) {
if (???username???){
        respond("error", "Sorry, the username ".$_POST['username']." is already in use. Please choose a different username.");}}
else if (???email???) {
    respond("error", "Sorry, the username ".$_POST['username']." is already in use. Please choose a different username.");}}

Answer 1

您可以尝试：

connect_db();
$check = mysql_query("SELECT 'User' validation
                        FROM school_users 
                       WHERE username = '$username' 
                       UNION ALL
                      SELECT 'Email' 
                        FROM school_users 
                       WHERE email = '$email'") or die(mysql_error());
$row = mysql_fetch_assoc($check);

if($row)
{
    if ($row["validation"] == 'User') {
            respond("error", "Sorry, the username ".$_POST['username']." is already in use. Please choose a different username.");}}
    else if ($row["validation"] == 'Email') {
        respond("error", "Sorry, the email ".$_POST['email']." is already in use. Please choose a different email.");}}
}

或者你可以单独做...

//Validate UserName
connect_db();
$check = mysql_query("SELECT username FROM school_users WHERE username = '$username'") or die(mysql_error());
$check2 = mysql_num_rows($check);

if ($check2 != 0) {
    respond("error", "Sorry, the username ".$_POST['username']." is already in use. Please choose a different username.");}

//Validate Email
connect_db();
$checkEmail = mysql_query("SELECT email FROM school_users WHERE email = '$email'") or die(mysql_error());
$checkEmail2 = mysql_num_rows($check);

if ($checkEmail2 != 0) {
    respond("error", "Sorry, the email ".$_POST['email']." is already in use. Please choose a different email.");}

此外，您的代码容易受到SQL注入攻击，并且您正在使用已弃用的MySQL php函数。如果您确实希望更好地使代码更容易受到攻击，请查看以下链接：

Why shouldn't I use mysql_* functions in PHP?

What could i use instead of mysql_ functions?

Prepated Statements

Prepared Statements with MySQLi

Answer 2

您也可以在一个声明中执行此操作：

SELECT username
FROM school_users
WHERE username = '$username' or  email = '$email'

如果您这样做，则需要将消息更改为用户。。。 “您的用户名或电子邮件（或两者）已在使用中。”

要在一个语句中自定义消息，您可以使用聚合：

select (case when max(username = '$username') = 1 and max(email = '$email' = 1
             then 'both'
             when max(username = '$username') = 1
             then 'username'
             when max(email = $email) = 1
             then 'email'
        end) as WherePresent
from school_users
WHERE username = '$username' or  email = '$email'

如果一切正常，则返回0行。否则，它返回一行“两者”，“用户名”，“电子邮件”，表示哪个是重复的。

我如何停止多个电子邮件或用户名？

2 个答案: