Handling Query Performance Issues | Dataford Interview Questions

What would you do if your query takes too long as there many rows of data

For this SQL exercise, write a PostgreSQL query that returns the requested metrics while demonstrating an approach suitable for large tables.

Output

One row per active seller and month for completed orders from 2024-01-01 through 2024-03-31.
Columns: month, seller_id, completed_orders, gmv, and previous_month_gmv.
Exclude inactive sellers, non-completed orders, and orders outside the date range. Orders with no item rows contribute zero GMV.
Sort by seller_id, then month ascending. Rows with a NULL previous_month_gmv are retained because they represent a seller's first available month.

sellers

orders

Column	Type	Description
order_idPK	INT	Order identifier
seller_id	INT	Seller responsible for the order
order_date	DATE	Order creation date
status	VARCHAR(30)	Current order status

order_items

Your question is Handling Query Performance Issues. Start with the requirements and the three tables in the Question tab.

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