php - MySQL-错误 : Unknown column in where clause

Question

<div class="ui-widget">

<form method="POST">
<?php

if(isset($_POST['search'])){

$connection = mysql_connect('localhost', 'root', '1234');
mysql_select_db('hoppers');

    $query = "SELECT user_name FROM users WHERE {$_POST['username']} = user_name";
    $result = mysql_query($query) or die ("MySQL-Error: " . mysql_error());
    $row = mysql_fetch_array($result);


if($row = TRUE){

        $present = $row['user_name'];
        echo $present;

     }else{
            echo "This User does not exist!";
        }
}
?>

<label for="tags">Username: </label>
<input type="text" id="tags" name = "username">
<input type="submit" name="search" value="Suchen!">
</form>
</div>

所以我总是收到此错误消息:MySQL-Error: Unknown column 'dompol171' in 'where Clause'.
因此，它将我输入的用户名与“user_name”列本身进行比较。我一直很害怕......因为我不知道如何以不同的方式比较它!

Answer 1

这里发生的情况是 $_POST['username'] 的值被视为一列，因为您没有引用它，即将其设置为字符串。假设用户名是 musa，它会尝试将 musa 列与 user_name 列进行比较(并且该列不存在)。应该是

 $query = "SELECT user_name FROM users WHERE 'some username' = user_name";