# Cross-Training Champions

THE GREAT DUCK MIGRATION! · challenge 11 · medium

> Captain Cosmos floats down with satellite weather data and route projections. "The migration path has drastically changed due to climate anomalies! We'll encounter flooded mountain passes requiring both swimming through valleys AND flying over peaks in rapid succession. Find athletes who've competed in BOTH swimming and flying_speed events - these rare amphibious champions can seamlessly transition between water and air. Sum their identification codes for the elite cross-training squadron registry!"

## Task

Return the sum of SSNs for all ducks who have competed in BOTH swimming and flying_speed events. You will be working with the `duck_athletes` and `performance_records` tables to find cross-training athletes.

## Tables

### `performance_records` (800 rows)

| column | type |
| --- | --- |
| duck_id | BIGINT |
| sport | VARCHAR |
| score | DOUBLE |
| competition_date | DATE |

### `duck_athletes` (50 rows)

| column | type |
| --- | --- |
| id | BIGINT |
| ssn | BIGINT |
| name | VARCHAR |
| age | BIGINT |
| hometown | VARCHAR |

## Data

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

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

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

Play it in the browser: https://dbquacks.com/challenges/athletic/11

## Answer

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