How can PHP developers ensure data normalization and efficient database design when implementing a rating system?

To ensure data normalization and efficient database design when implementing a rating system in PHP, developers should use a separate table to store ratings, with columns for the user ID, item ID, and rating value. This allows for easy retrieval and manipulation of ratings data without duplicating information. Additionally, developers should consider indexing the columns used for querying ratings to improve performance.

// Create a ratings table in the database
CREATE TABLE ratings (
    id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT,
    item_id INT,
    rating INT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

// Insert a new rating into the ratings table
INSERT INTO ratings (user_id, item_id, rating)
VALUES (1, 123, 5);

// Retrieve ratings for a specific item
SELECT * FROM ratings WHERE item_id = 123;

// Retrieve average rating for an item
SELECT AVG(rating) AS average_rating FROM ratings WHERE item_id = 123;