What best practices should be followed when structuring and optimizing PHP code for database queries involving multiple tables?

When structuring and optimizing PHP code for database queries involving multiple tables, it is essential to use proper SQL JOINs to efficiently retrieve data from related tables in a single query. Additionally, utilizing indexes on the columns involved in JOIN conditions can significantly improve query performance. It is also recommended to sanitize user inputs to prevent SQL injection attacks and to properly handle errors to ensure robustness in the code. 

// Example PHP code snippet for querying multiple tables using JOIN and handling errors

$query = "SELECT users.id, users.username, orders.order_id FROM users 
          JOIN orders ON users.id = orders.user_id 
          WHERE users.id = :user_id";

try {
    $stmt = $pdo->prepare($query);
    $stmt->bindParam(':user_id', $user_id, PDO::PARAM_INT);
    $stmt->execute();
    
    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
    
    // Process the query result here
} catch (PDOException $e) {
    // Handle any errors that occur during the query execution
    echo "Error: " . $e->getMessage();
}

Keywords

SQL joins indexes query optimization Eloquent ORM database normalization

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