This works:
select product_id, count(*) from order_line group by product_id

It shows the product and how many sales each product has.

However, I want to sort by the product sales, so I am trying:
select product_id, count(*) from order_line group by product_id order by count(*)

It doesn't like "order by count(*)". I tried many variations and just couldn't figure out how to make it sort by the count

Of course, "orber by product_id" would work.

How do I make it sort by the COUNT()?

By the way, I am using MySQL

SELECT product_id, count(*) AS total
FROM order_line
GROUP BY product_id
ORDER BY total

Thanks. Exactly what I needed.