Weekly Active Purchaser Growth Rate

ShopWave wants to track how its active purchaser base changes week over week. Write a PostgreSQL query to calculate the weekly count of active purchasers and the week-over-week growth rate.

An active purchaser is a user who has at least one completed transaction in a given calendar week. Use the transaction date to assign each purchase to a week.

Requirements

1. Count distinct purchasers per week using only transactions with status = 'completed'.
2. Return one row per week, even if there are zero active purchasers that week.
3. Calculate the prior week's active purchaser count.
4. Compute week-over-week growth rate as: ((current_week_active_purchasers - previous_week_active_purchasers) / previous_week_active_purchasers) * 100 Return NULL when the previous week is 0 or missing.
5. Order the output by week start date ascending.

Table Definitions

transactions

users