# Roll Call Across Worlds

THE CLOUD EXPEDITION! · level 8 · chapter 3

Captain Cloudsworth rises to full height, wings spread wide. 'THREE ecosystems. THREE public research datasets — open to any duck on MotherDuck!' He looks down at you with a conspiratorial grin. 'Attach them all and find out which species have conquered multiple worlds.' Time for <span class='feature-highlight'>Multi-Share Analytics</span> — attaching and querying across multiple public shared databases.

## Task

Attach the remaining two shared databases, then combine species data from all three to find which species span multiple ecosystems. Return <b>species_name</b>, <b>num_ecosystems</b>, and <b>total_population</b> — most widespread first, then by total population. Tables: <code>dbquacks_marina_lake.species</code> (attached in level 7), <code>dbquacks_arctic_pond.species</code>, <code>dbquacks_tropical_lagoon.species</code>. Each has <code>species_name</code> and <code>population_count</code> columns. Run the ATTACH commands before your SELECT — all statements together.<br><br><b>Share URLs:</b><ul><li><code>dbquacks_arctic_pond</code> → <code>md:_share/arctic_pond_db/35caa010-56d6-465b-80f2-5d67270ec0ed</code></li><li><code>dbquacks_tropical_lagoon</code> → <code>md:_share/tropical_lagoon_db/7e2b85ab-5af9-496a-870c-c7e0e20e1c65</code></li></ul><br><b>About MotherDuck shares:</b> Shares have three access levels: <b>UNRESTRICTED</b> (public — anyone can attach), <b>ORGANIZATION</b> (your team only), and <b>RESTRICTED</b> (explicit grants needed). These tutorial datasets use UNRESTRICTED access.

## Hint

ATTACH the two new shared databases the same way, then use UNION ALL to stack all three species tables together

## Expected result

Rows with columns: species_name, num_ecosystems, and total_population — ordered by num_ecosystems descending

## 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_marina_lake.species`

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

### `dbquacks_arctic_pond.species`

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

### `dbquacks_tropical_lagoon.species`

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/8

## Reference

https://motherduck.com/docs/key-tasks/sharing-data/sharing-overview/