Add back-end database to web front-end

With the rapid development of the Internet, more and more companies and institutions have begun to pay attention to the construction and development of websites, and the web front-end, as the face of the website, plays a vital role in user experience and page display. However, a website with only front-end cannot meet the needs of users. A lot of information and interactions need to be realized through the back-end database. Therefore, front-end engineers need to master the knowledge of how to increase the back-end database in order to better complete the development of the website.

1. The role of the backend database

The website not only needs to display information to users through the UI interface, but also needs to store and process a large amount of data, which can be used for member management, order processing, content publishing and many other aspects. The backend database is where these data are stored and is responsible for transmitting data from the front-end page to the server for management and maintenance.

There are many types of backend databases, such as MySQL, Oracle, SQL Server, MongoDB, etc. Among them, MySQL is more commonly used because it is simple to use, has good compatibility, and has high stability.

2. Connecting to the back-end database

In the web front-end, to access the back-end database, you need to use an intermediate technology, usually a back-end language such as PHP, Java, ASP.NET. The following is an example of PHP code to connect to the MySQL database:

//连接数据库
$con = mysqli_connect('localhost','root','','test');
//设置编码格式
mysqli_set_charset($con,"utf8");
//检查连接是否成功
if (!$con) {
    die('Connect Error (' . mysqli_connect_errno() . ') ' . mysqli_connect_error());
}

The above code first uses the mysqli_connect() function to connect to the local MySQL database, then uses the mysqli_set_charset() function to set the database encoding to utf8, and finally checks whether the connection is successful through the if statement success. If the connection is unsuccessful, program execution is stopped and an error message is returned.

3. Add, delete, modify and query data

After connecting to the backend database, the front end needs to be able to perform add, delete, modify and query operations on the data in the database. The following uses PHP as an example to introduce how to implement these operations:

1. Insert data

$name = $_POST['name'];
$age = $_POST['age'];
$sex = $_POST['sex'];
$insert = "INSERT INTO user (name, age, sex) VALUES ('$name', '$age', '$sex')";
if ($con->query($insert) === TRUE) {
    echo "插入成功！";
} else {
    echo "Error: " . $insert . "<br>" . $con->error;
}

The above code uses SQL statements to insert data from the front end into the user of the MySQL database table. Notice that the three variables $name, $age, and $sex are POST data obtained from the form.

2. Delete data

$id = $_GET['id'];
$delete = "DELETE FROM user WHERE id=$id";
if ($con->query($delete) === TRUE) {
    echo "删除成功！";
} else {
    echo "Error: " . $delete . "<br>" . $con->error;
}

The above code uses SQL statements to delete the data with ID $id from the user table of the MySQL database. The $id variable is the GET data obtained from the URL.

3. Modify data

$id = $_POST['id'];
$name = $_POST['name'];
$age = $_POST['age'];
$sex = $_POST['sex'];
$update = "UPDATE user SET name='$name', age='$age', sex='$sex' WHERE id=$id";
if ($con->query($update) === TRUE) {
    echo "修改成功！";
} else {
    echo "Error: " . $update . "<br>" . $con->error;
}

The above code uses SQL statements to modify the data with ID $id in the user table of the MySQL database.

4. Query data

$sql = "SELECT * FROM user";
$result = mysqli_query($con,$sql);

if (mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        echo "ID:".$row["id"]." - Name:".$row["name"]." - Age:".$row["age"]." - Sex:".$row["sex"]."<br>";
    }
} else {
    echo "0 结果";
}
mysqli_close($con);

The above code uses SQL statements to query all data in the user table of the MySQL database and displays the results on the web page.

4. Summary

In modern web front-end development, connecting to the backend database is a necessary step. Only when the connection is established and the operation of the database is implemented, can the website truly realize its functions and values. promote. Therefore, front-end engineers need to strengthen their study and practice of back-end databases, master basic operations such as connections, additions, deletions, modifications, etc., and constantly improve their skills to provide effective support for website development.

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