In PHP, how can JOIN statements be used to combine tables for more efficient querying?

When querying data from multiple tables in a database, JOIN statements can be used in PHP to combine the tables based on a related column, allowing for more efficient querying by reducing the number of separate queries needed. By joining tables together, you can retrieve all the necessary data in one go, rather than making multiple queries and then combining the results in your PHP code. 

<?php

// Establish a connection to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// Query using JOIN statement to combine tables
$sql = "SELECT orders.order_id, customers.customer_name
        FROM orders
        INNER JOIN customers ON orders.customer_id = customers.customer_id";

$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Output data of each row
    while($row = $result->fetch_assoc()) {
        echo "Order ID: " . $row["order_id"]. " - Customer Name: " . $row["customer_name"]. "<br>";
    }
} else {
    echo "0 results";
}

$conn->close();

?>

Keywords

PHP JOIN statements tables querying efficiency

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