A data engineer runs the following SQL query on an orders table. What does it return?

```sql
SELECT customer_id, order_date, amount,
ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn
FROM orders
```

Question

A data engineer runs the following SQL query on an orders table. What does it return?

```sql
SELECT customer_id, order_date, amount,
  ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn
FROM orders
```

Accepted Answer

B. A sequential row number for each order within each customer partition, with the most recent order numbered 1. `ROW_NUMBER()` assigns a unique sequential integer to each row within a window partition. `PARTITION BY customer_id` creates a separate numbering sequence for each customer. `ORDER BY order_date DESC` ensures the most recent order for each customer receives the value 1.

A data engineer runs the following SQL query on an orders table. What does it return?
`SELECT customer_id, order_date, amount, ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn FROM orders`

Related Questions

Discussion

A data engineer runs the following SQL query on an orders table. What does it return? SELECT customer_id, order_date, amount, ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn FROM orders

Related Questions

Discussion

A data engineer runs the following SQL query on an orders table. What does it return?
`SELECT customer_id, order_date, amount, ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn FROM orders`