Mastering PHP’s mysqli_query: Quick Guide to SELECT, INSERT, UPDATE, DELETE

MySQL is a widely used relational database management system, and PHP provides functions to connect and operate on MySQL databases. The mysqli_query function is a common way to execute queries such as SELECT, INSERT, UPDATE, and DELETE.

The following example demonstrates how to create a MySQL connection with mysqli_connect, run a SELECT query using mysqli_query, check for errors, fetch rows with mysqli_fetch_assoc, and output each record’s ID, name, and age.

<?php
// Create database connection
$connection = mysqli_connect('localhost', 'username', 'password', 'database');

// Check connection
if (!$connection) {
    die('Database connection failed: ' . mysqli_connect_error());
}

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

// Check query success
if (!$result) {
    die('Query failed: ' . mysqli_error($connection));
}

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

// Free result set
mysqli_free_result($result);

// Close connection
mysqli_close($connection);
?>

The code first creates and verifies the database connection, then stores the SELECT result in $result. It iterates over $result to print each row’s fields, finally freeing the result set and closing the connection.

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

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

In summary, using PHP’s mysqli_query provides a convenient and fast way to perform MySQL operations, whether selecting, inserting, updating, or deleting data.