Introduction
Very simple subqueries
Subqueries with multiple results
Correlated subqueries
14. The operator IN with correlated subqueries
Other subqueries

## Instruction

Wow, cool! Now, remember the operator IN? It allowed us to specify a few values in the WHERE clause, so it worked a bit like the OR operator. Now, take a look:

SELECT
*
FROM city
WHERE country_id IN (
SELECT id FROM country
WHERE id = city.country_id
AND country.population < 40000
);


Can you predict what the above instruction does? It shows all cities from such countries where the total population of the country is less than 40 000.

## Exercise

Show all information about all trips to cities with their rating lower than 4.

### Stuck? Here's a hint!

Type:

SELECT
*
FROM trip
WHERE city_id IN (
SELECT id FROM city
WHERE id = trip.city_id AND rating < 4
);