Using PHP mysqli_query to Execute MySQL Queries

MySQL is a widely used relational database management system, and when developing web applications it is common to execute various queries. PHP, a popular server‑side language, offers many functions for connecting to and operating MySQL databases, among which the mysqli_query function is frequently used to run queries.

The mysqli_query function can execute all types of MySQL statements, including SELECT, INSERT, UPDATE, and DELETE. It takes two arguments: the database connection object and the SQL query string. The following example demonstrates using mysqli_query to perform 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 script first creates a database connection and verifies its success. It then runs a SELECT statement with mysqli_query, storing the result in the $result variable. By looping over $result with mysqli_fetch_assoc, each row’s ID, name, and age are printed. Finally, the result set is freed and the connection closed.

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

Note that mysqli_query returns a result‑set object for queries that produce results. You can retrieve rows using functions like mysqli_fetch_assoc, mysqli_fetch_row, or mysqli_fetch_array, depending on the desired format.

In summary, the PHP mysqli_query function provides a convenient way to interact with MySQL databases for a variety of operations, making it easy to perform SELECT, INSERT, UPDATE, and DELETE tasks.