PHP database connection tutorial: beginner to database management master

To connect to the MySQL database, you need to create a database connection and use SQL queries to perform data operations (including retrieval, insertion, update, and deletion). Practical case demonstrates how to connect to a MySQL database and retrieve usernames. Specific steps include: creating a connection, executing the query, traversing the result set and printing the data.

PHP Database Connection Tutorial: Beginner to Database Management Master

Prerequisite

• PHP is installed on the local computer
• Database management system (such as MySQL, PostgreSQL or MariaDB)

1. Create a database connection

<?php
// 数据库主机名
$hostname = 'localhost';
// 数据库用户名
$username = 'db_username';
// 数据库密码
$password = 'db_password';
// 数据库名称
$database = 'db_name';

// 连接到数据库
$conn = mysqli_connect($hostname, $username, $password, $database);
?>

2. Execute the SQL query

Once established Once connected, you can execute SQL queries.

<?php
// 查询字符串
$query = "SELECT * FROM table_name";

// 执行查询
$result = mysqli_query($conn, $query);

// 遍历结果集
while($row = mysqli_fetch_assoc($result)) {
    echo $row['column_name'];
}
?>

3. Insert data

<?php
// 插入数据
$query = "INSERT INTO table_name (column1, column2) VALUES ('value1', 'value2')";

// 执行查询
mysqli_query($conn, $query);
?>

4. Update data

<?php
// 更新数据
$query = "UPDATE table_name SET column1 = 'new_value' WHERE id = 1";

// 执行查询
mysqli_query($conn, $query);
?>

5. Delete data

<?php
// 删除数据
$query = "DELETE FROM table_name WHERE id = 1";

// 执行查询
mysqli_query($conn, $query);
?>

Practical case: Connect to MySQL database

Suppose you have a MySQL database named "users" and a table named "user_table" that contains usernames and passwords. Here's how to connect to that database and retrieve the username:

<?php
// 连接到 MySQL 数据库
$conn = mysqli_connect('localhost', 'root', '', 'users');

// 查询 user_table
$query = "SELECT username FROM user_table";

// 执行查询
$result = mysqli_query($conn, $query);

// 遍历结果集并打印用户名
while($row = mysqli_fetch_assoc($result)) {
    echo $row['username'] . PHP_EOL;
}
?>

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