EPAM Systems wants a daily revenue view for products sold through its digital services portfolio. Write a PostgreSQL query that reports revenue by product and date for the reporting period from 2025-01-01 through 2025-01-04.
daily_revenue as quantity * unit_price, counting only sales with status = 'completed'. Treat missing revenue as zero.running_total separately for each product, ordered chronologically.daily_change as the difference between the current day's revenue and the previous day's revenue for that product. Return NULL for the first date.| Column | Type | Description |
|---|---|---|
| category_idPK | INT | Category identifier |
| category_name | VARCHAR(100) | Category name |
| Column | Type | Description |
|---|---|---|
| product_idPK | INT | Product identifier |
| product_name | VARCHAR(150) | Product name |
| category_id | INT | References categories.category_id |
| Column | Type | Description |
|---|---|---|
| sale_idPK | INT | Sale identifier |
| product_id | INT | References products.product_id |
| sale_date | DATE | Date on which the sale occurred |
| quantity | INT | Number of units sold |
| unit_price | NUMERIC(10,2) | Price per unit |
| status | VARCHAR(20) | Sale processing status |