Using PHP mysqli_query to Execute MySQL Queries

MySQL is a widely used relational database management system, and when developing web applications PHP provides functions to connect and operate MySQL databases, among which the mysqli_query function is commonly used to execute queries.

The mysqli_query function can run SELECT, INSERT, UPDATE, DELETE and other SQL statements; it takes a database connection object and a query string as parameters. Below is a complete example that demonstrates 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 creates a connection, checks it, runs the SELECT statement, stores the result in $result, iterates over each row to output ID, name, and age, then frees the result set and closes the connection.

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

When mysqli_query runs a query, it returns a result set object; functions like mysqli_fetch_assoc, mysqli_fetch_row, and mysqli_fetch_array can be used to retrieve rows in different formats.

In summary, using PHP’s mysqli_query to perform MySQL operations is convenient and efficient for SELECT, INSERT, UPDATE, and DELETE tasks.

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