What is the purpose of using JOIN in MySQL queries?

When working with relational databases like MySQL, JOIN is used to combine rows from two or more tables based on a related column between them. This allows us to retrieve data from multiple tables in a single query, avoiding the need for multiple separate queries. JOIN helps in fetching related data efficiently and effectively, making it a powerful tool for querying databases. 

<?php
// Establish a connection to the MySQL 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);
}

// SQL query using JOIN to retrieve data from multiple tables
$sql = "SELECT orders.order_id, customers.customer_name
        FROM orders
        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

MySQL JOIN queries PHP purpose

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