Use the PHP function 'mysqli_query' to execute MySQL queries

Use PHP function "mysqli_query" to execute MySQL queries

MySQL is a widely used relational database management system. When developing Web applications, it is often necessary to perform various query operations. As a commonly used server-side programming language, PHP provides a variety of functions to connect and operate the MySQL database. Among them, the "mysqli_query" function is one of the commonly used functions to perform query operations.

The "mysqli_query" function can execute various types of MySQL query statements, including SELECT, INSERT, UPDATE, DELETE, etc. It accepts two parameters, the first parameter is the database connection object, and the second parameter is the query statement to be executed. The following is a sample code that uses the "mysqli_query" function to execute 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 above code first creates a database connection object and checks whether the connection is successful. Then, a SELECT query is executed using the "mysqli_query" function, and the query results are saved in the $result variable. Next, loop through the data in the $result variable and print out the ID, name, and age of each row. Finally, the query result set is released and the database connection is closed.

In addition to executing SELECT queries, the "mysqli_query" function can also execute other types of queries. For example, you can use this function to execute an INSERT statement to insert data into the database, use an UPDATE statement to update data in the database, use a DELETE statement to delete data in the database, and so on. Just pass in the corresponding SQL statement as the second parameter of the "mysqli_query" function.

It should be noted that when the "mysqli_query" function executes a query statement, it returns a result set object. By traversing this result set object, you can obtain each row of data in the query results. You can use "mysqli_fetch_assoc", "mysqli_fetch_row", "mysqli_fetch_array" and other functions to obtain different forms of query results.

In summary, it is very convenient and fast to use the PHP function "mysqli_query" to execute MySQL queries. Whether you are performing SELECT, INSERT, UPDATE or DELETE operations, you only need to pass in the corresponding query statement to easily operate the database.

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