PhP & MySQL WHERE 语法答案

【问题标题】：PhP & MySQL WHERE SyntaxPhP & MySQL WHERE 语法
【发布时间】：2019-12-03 15:50:18
【问题描述】：

有一个注册界面，您必须在登录后输入您的账单信息。目标是在 MySQL 数据库中记录输入的数据并将“计费”值更新为“1”，但是出现语法错误。

代码是（PhP 7.3）：

<?php

session_start();
if(!isset($_SESSION['username'])) {
    header('location: login.php');
    exit();
}

include_once('dbconnect.php');

$username = $_SESSION["username"];
$result = mysqli_query($conn, "SELECT * FROM users WHERE username = '$username'");
while($row = mysqli_fetch_array($result)) {

    if ($row['billable'] == 0) {

        $error = false;
        if(isset($_POST['btn-updatedetails'])) {

        $firstname = mysqli_real_escape_string($conn, $_REQUEST['firstname']);
        $lastname = mysqli_real_escape_string($conn, $_REQUEST['lastname']);
        $phone = mysqli_real_escape_string($conn, $_REQUEST['phone']);
        $company = mysqli_real_escape_string($conn, $_REQUEST['company']);
        $country = mysqli_real_escape_string($conn, $_REQUEST['country']);
        $county = mysqli_real_escape_string($conn, $_REQUEST['county']);
        $city = mysqli_real_escape_string($conn, $_REQUEST['city']);
        $street = mysqli_real_escape_string($conn, $_REQUEST['street']);
        $postcode = mysqli_real_escape_string($conn, $_REQUEST['postcode']);

        if(empty($firstname)) {
            $error = true;
            $errorFirstname = 'This field cannot be left blank.';
        }    

        if(empty($lastname)) {
            $error = true;
            $errorLastname = 'This field cannot be left blank.';
        } 

        if(empty($phone)) {
            $error = true;
            $errorPhone = 'This field cannot be left blank.';
        }  

        if(empty($country)) {
            $error = true;
            $errorCountry = 'This field cannot be left blank.';
        } 

        if(empty($county)) {
            $error = true;
            $errorCounty = 'This field cannot be left blank.';
        } 

        if(empty($city)) {
            $error = true;
            $errorCity = 'This field cannot be left blank.';
        } 

        if(empty($street)) {
            $error = true;
            $errorStreet = 'This field cannot be left blank.';
        } 

        if(empty($postcode)) {
            $error = true;
            $errorPostcode = 'This field cannot be left blank.';
        } 

        if(!$error){
            $sql = "INSERT INTO users (firstname, lastname, phone, company, country, county, city, street, postcode) VALUES ('$firstname', '$lastname', '$phone', '$company', '$country', '$county', '$city', '$street', '$postcode') WHERE username = '$username' AND UPDATE users SET billable='1' WHERE username = '$username'";
            if(mysqli_query($conn, $sql)){
                $successMsg = 'Success!';
            }else{
                echo 'Error '.mysqli_error($conn);
            }

        }

    }

        ?>
        <form method="POST" action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']); ?>" autocomplete="off">
        Firstname:
        <input type="text" name="firstname" id="firstname"><br>
        Lastname:
        <input type="text" name="lastname" id="lastname"><br>
        Phone:
        <input type="text" name="phone" id="phone"><br>
        Company (optional):
        <input type="text" name="company" id="company"><br>
        Country:
        <input type="text" name="country" id="country"><br>
        County:
        <input type="text" name="county" id="county"><br>
        City:
        <input type="text" name="city" id="city"><br>
        Street:
        <input type="text" name="street" id="street"><br>
        Postcode:
        <input type="text" name="postcode" id="postcode"><br>

        <input type="submit" name="btn-updatedetails">
        </form>

        <?php


} else {
        echo "<3";
    }
}

mysqli_close($conn);

此页面返回以下错误：

Error You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE username = 'Erik' AND UPDATE users SET billable='1' WHERE username = 'Erik' at line 1

MySQL 数据库：

我在哪里做错了？

提前感谢您的回答！
祝你有美好的一天！

【问题讨论】：

你为什么要这样做？ UPDATE users SET billable='1' WHERE username = '$username'"
@Regolith 同样的问题。
插入语句中不需要where
好的。我删除了第一个 WHERE。当前代码：$sql = "INSERT INTO users (firstname, lastname, phone, company, country, county, city, street, postcode) VALUES ('$firstname', '$lastname', '$phone', '$company', '$country', '$county', '$city', '$street', '$postcode') AND UPDATE users SET billable='1' WHERE username = '$username'"; 现在我收到以下错误：“错误您的 SQL 语法有错误；请查看与您的 MariaDB 服务器版本相对应的手册以获取正确的语法以在 'AND UPDATE users SET billable 附近使用='1' WHERE 用户名 = 'Erik'' 在第 1 行“
我想你明白你可以直接在 1 处插入计费属性？或者在您的架构中使用默认值。为什么之后更新？

标签： php mysql syntax insert

【解决方案1】：

您从 SELECT 开始，所以我不明白您为什么要为同一用户在另一行 INSERT。我想你只想像这样做一个UPDATE：

UPDATE users 
SET
    firstname = '$firstname',
    lastname = '$lastname',
    phone = '$phone',
    company = '$company',
    country = '$country',
    county = '$county',
    city = '$city',
    street = '$street',
    postcode = '$postcode',
    billable = 1
WHERE username = '$username'

【讨论】：