How can SQL joins be utilized to optimize the retrieval of data from multiple tables in PHP?

When retrieving data from multiple tables in a database using PHP, SQL joins can be utilized to optimize the process by combining related data from different tables into a single result set. By using SQL joins, you can avoid making multiple queries and fetching data separately, which can improve performance and reduce the number of database calls. 

<?php
// Establish a connection to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

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

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

// SQL query with INNER JOIN to retrieve data from multiple tables
$sql = "SELECT users.username, orders.order_id, orders.total_amount
        FROM users
        INNER JOIN orders ON users.user_id = orders.user_id";

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

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

$conn->close();
?>

Keywords

SQL joins data retrieval multiple tables optimization PHP

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