# Two Engines, One Query

THE CLOUD EXPEDITION! · level 19 · chapter 7

Dr. Velocity revs two imaginary engines. 'Ladies and gentleducks, welcome to the DUAL EXECUTION DERBY! Your laptop and MotherDuck's cloud, racing in PARALLEL!' Captain Cloudsworth drops an imaginary checkered flag. 'But HOW does it decide what runs where? Let's peek under the hood.' Discover <span class='feature-highlight'>Dual Execution</span> — using EXPLAIN to see how MotherDuck splits work between local and cloud engines.

## Task

Peek under the hood of a hybrid query. Use `EXPLAIN` on a query that joins local `pondville_residents` with cloud `dbquacks_cloud_expedition.duck_travels` to see how MotherDuck splits work between your laptop and the cloud. Tables: `pondville_residents` (local), `dbquacks_cloud_expedition.duck_travels` (MotherDuck, linked by `duck_id`).

## Hint

Prefix your query with EXPLAIN to see how DuckDB splits work between local and cloud

## Expected result

An execution plan showing how MotherDuck splits the query between local and cloud operators

## Tables

### `lake_visits` (500 rows)

| column | type |
| --- | --- |
| visit_id | BIGINT |
| duck_id | BIGINT |
| destination_pond | VARCHAR |
| visit_date | DATE |
| purpose | VARCHAR |

### `pondville_events` (50 rows)

| column | type |
| --- | --- |
| event_id | BIGINT |
| event_name | VARCHAR |
| event_date | DATE |
| organizer_id | BIGINT |
| location | VARCHAR |
| attendee_count | BIGINT |

### `pondville_residents` (100 rows)

| column | type |
| --- | --- |
| duck_id | BIGINT |
| name | VARCHAR |
| species | VARCHAR |
| home_pond | VARCHAR |
| age | BIGINT |
| occupation | VARCHAR |
| joined_date | DATE |

### `dbquacks_cloud_expedition.duck_travels`

A table in a MotherDuck share; its columns are not listed here.

## Data

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

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

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

This level also queries MotherDuck shares, which need a MotherDuck token. On the page, the editor asks for one.

Play it in the browser: https://dbquacks.com/motherduck/19

## Reference

https://motherduck.com/docs/key-tasks/running-hybrid-queries/