Month-over-month revenue growth

Medium41% solve itAsked at Amazon, Walmart, PayPal

Return revenue per month and the percentage change against the previous month. The first month has no previous month, so its growth is null. Months with no orders must still appear with zero revenue.

Input schema

orders order_id bigint ordered_at timestamp amount numeric status string -- 'PAID' | 'REFUNDED' | 'CANCELLED'

Constraints

Only PAID orders count toward revenue
growth_pct rounded to two decimal places
Gap months between the first and last order month must be present
Output ordered by month ascending
When the previous month's revenue is 0, growth_pct is null — a percentage change from zero is undefined

Example 1growth against the previous month

Input · orders

amount	status	order_id	ordered_at
10000	PAID	1	2024-01-15 00:00:00
12500	PAID	2	2024-02-10 00:00:00

Output

month	revenue	growth_pct
2024-01	10000	null
2024-02	12500	25

Example 2only PAID orders count