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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 country.population < 40000
);


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

## Exercise

Show all information about all trips to cities which have a rating lower than 4.

### Stuck? Here's a hint!

Type:

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