# THE DOUBLE DIP

WEEKLY QUACK CHALLENGE! · challenge 15 · medium · 5 guesses

> Refund Clerk Redhead slides a ledger across the counter. "Returns are fine, Duckbert. Paying a duck back more than they paid for an order is less fine. Pearl returned half the shop, Betty paid in three installments, and somebody swears their other purchases should make us even. I need the customer who collected the most excess refunds across their orders. Somebody's left with their bread and ours — find them before I balance this till!"

## Task

Return the customer name with the largest total excess refund. For each order, total its `succeeded` payments and its `succeeded` refunds; `failed` and `pending` attempts do not count. Count every successful row, even when two share an amount, and an order with no successful payment has been paid zero. An order's excess is how much its refunds exceed its payments, or zero if they do not. Add up the excess across each customer's orders. On a tie, return the alphabetically first customer name. You will be working with the `orders`, `payments`, and `refunds` tables.

## Tables

### `orders` (14 rows)

| column | type |
| --- | --- |
| order_id | INTEGER |
| customer_name | VARCHAR |

### `payments` (21 rows)

| column | type |
| --- | --- |
| payment_id | INTEGER |
| order_id | INTEGER |
| amount | DECIMAL(10,2) |
| status | VARCHAR |

### `refunds` (16 rows)

| column | type |
| --- | --- |
| refund_id | INTEGER |
| order_id | INTEGER |
| amount | DECIMAL(10,2) |
| status | VARCHAR |

## Data

The tables live in a DuckDB database: https://dbquacks.com/data/databases/weekly_202641_15_double_dip.duckdb

To query it outside the browser, attach it read-only:

```sql
ATTACH 'https://dbquacks.com/data/databases/weekly_202641_15_double_dip.duckdb' AS db (READ_ONLY);
USE db;
```

Play it in the browser: https://dbquacks.com/challenges/weekly/15

## Answer

The expected answer is not published. Submit on the page to have it checked.