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 execute various queries. PHP, a common server‑side language, provides many functions to connect to and operate MySQL databases, among which the mysqli_query function is frequently used for executing queries.

The mysqli_query function can run different types of MySQL statements such as SELECT, INSERT, UPDATE, and DELETE. It requires 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 code first creates a database connection and verifies it, then executes a SELECT statement with mysqli_query, stores the result in $result, iterates over the result set to output each row’s ID, name, and age, and finally frees the result set and closes the connection.

Beyond SELECT, mysqli_query can execute other statements such as INSERT to add records, UPDATE to modify them, and DELETE to remove them, simply by passing the appropriate SQL as the second argument.

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

In summary, using PHP’s mysqli_query function to interact with MySQL is convenient and efficient for performing SELECT, INSERT, UPDATE, or DELETE operations.

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