One solution could be to use a separate table to store the product categories and their associations with the products. This table could have columns for the product ID and category ID, allowing for efficient querying and filtering.
To populate this table, you could write a script that loops through all the products and their categories, and inserts the appropriate records into the new table.
Then, when a user selects a category to filter by, you can query the new table to get all the product IDs associated with that category, and use those IDs to retrieve the relevant products from the main products table.
Here's an example of how you could structure the new table:
CREATE TABLE product_categories (
id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
product_id INT UNSIGNED NOT NULL,
category_id INT UNSIGNED NOT NULL,
INDEX product_category_index (product_id, category_id)
);
And here's an example of how you could query the table to get all the product IDs associated with a given category:
SELECT product_id FROM product_categories WHERE category_id = :category_id;