尝试检查是否已存在具有相同值的电子邮件

Question

我正在尝试这样做，以便在将数据插入数据库之前检查电子邮件是否已存在于数据库中。

这是我的代码：

<?php
    $servername = "servername";
    $username = "username";
    $password = "password";
    $dbname = "dbname";

    $Mail = $_POST['email'];

    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);

    // Check connection
    if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
    }

    //Inputed in E-Mail Field
    $Mail = $_POST['email'];

    $SearchEmail = $conn->query("SELECT (Mail) FROM betakey WHERE Mail = '$Mail'");

    if ($SearchEmail->num_rows > 0) {
        print "That Email is already registered for the closed alpha";
    }
    else {
        $conn->query("INSERT INTO betakey VALUES ('$Mail')");
    }

    $conn->close();
    ?> 

当我访问该页面时它不会给我任何错误，但它也不会回显它存在或在它不存在时插入数据。

Answer 1

问题出在您的插入查询中。插入查询的结构始终如下所示。

INSERT INTO table_name (column1, column2, column3,...) 值（值 1，值 2，值 3，...） 见：http://www.w3schools.com/php/php_mysql_insert.asp

将此应用于您的代码，结果如下。

<?php
$servername = "servername";
$username = "username";
$password = "password";
$dbname = "dbname";

$Mail = $_POST['email'];

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}

//Inputed in E-Mail Field
$Mail = $_POST['email'];

$SearchEmail = $conn->query("SELECT count(Mail) FROM betakey WHERE Mail = '$Mail'");

if ($SearchEmail->num_rows > 0) {
    print "That Email is already registered for the closed alpha";
}
else {
    $conn->query("INSERT INTO betakey (Mail) VALUES ('$Mail')");
}

$conn->close();
?> 

而且我建议你去掉两个'$Mail = $_POST['email'];'中的一个，因为以同样的方式声明一个变量两次是没有用的。