Using PHP mysqli_query to Execute MySQL Queries

MySQL is a widely used relational database management system, and when developing web applications developers often need to perform various queries. PHP, a common server‑side language, provides functions to connect to and operate MySQL databases, with mysqli_query being a primary function for executing queries.

The mysqli_query function can execute many types of MySQL statements, including SELECT, INSERT, UPDATE, and DELETE. It accepts two parameters: the database connection object and the SQL query string. Below is an example that performs a SELECT query.

<?php
// 创建数据库连接
$connection = mysqli_connect('localhost', 'username', 'password', 'database');

// 检查连接是否成功
if (! $connection) {
    die('数据库连接失败: ' . mysqli_connect_error());
}

// 执行SELECT查询
$query = "SELECT id, name, age FROM users";
$result = mysqli_query($connection, $query);

// 检查查询是否成功
if (! $result) {
    die('查询失败: ' . mysqli_error($connection));
}

// 处理查询结果
while ($row = mysqli_fetch_assoc($result)) {
    echo 'ID: ' . $row['id'] . ', 姓名: ' . $row['name'] . ', 年龄: ' . $row['age'] . '<br>';
}

// 释放结果集
mysqli_free_result($result);

// 关闭数据库连接
mysqli_close($connection);
?>

The example code first creates a database connection and checks its success, then runs a SELECT query and stores the result in $result. It iterates over $result to output each row’s ID, name, and age, finally freeing the result set and closing the connection.

Beyond SELECT, mysqli_query can execute other statements such as INSERT, UPDATE, and DELETE by passing the appropriate SQL as the second argument.

It is important to note that mysqli_query returns a result set object for SELECT queries; you can retrieve rows using functions like mysqli_fetch_assoc, mysqli_fetch_row, or mysqli_fetch_array to obtain different result formats.

In summary, using PHP’s mysqli_query function provides a convenient and efficient way to perform common database operations, making it a valuable tool for backend developers working with MySQL.