Month-over-month revenue growth

Table orders:

For each month that has orders, return the revenue and its growth in percent compared with the previous calendar month:

growth_pct = (revenue - previous_revenue) / previous_revenue * 100, rounded to 2 decimals.

growth_pct is NULL when the previous calendar month has no orders, or when its revenue is 0.

Output columns: month (text YYYY-MM), revenue, growth_pct. Order by month.

CREATE TABLE orders (
  id int PRIMARY KEY,
  amount int NOT NULL,
  created_at timestamp NOT NULL
);