SQL: What country has the most cities?

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Hello I started using MySQL and I seem to be having trouble trying to nest formulas. I'm working on a problem and the question is, What country has the most cities?

I have two tables:

CITY:
city
city_id
country_id

COUNTRY:
country 
country_id

I am able to join the two tables together to get the cities to match with the countries but after that I don't know how to count to the country that has the most cities.

My current code is:

SELECT city.city, country.country 
FROM city, country
WHERE city.country_id = country.country_id

From there I don't know how to add a count function without it coming back as as error. I dont fully understand the basics of nesting.

Thank you, any help is appreciated.

Try following Code -

SELECT *, 
  (SELECT COUNT(*) FROM cities WHERE cities.country_id=C.country_id) as cities_count 
FROM country C 
ORDER BY cities_count DESC
LIMIT 0,1

Also is joining the two tables necessary? In your query, you said you need to find What country has the most cities?

Above query will only return one country with max cities.

queries, This is a list of the SQL queries we executed in class Find all countries in Europe that have *some* city with population -- more than 5 million SELECT C. Name� city_id: A surrogate primary key used to uniquely identify each city in the table. city: The name of the city. country_id: A foreign key identifying the country that the city belongs to. last_update: When the row was created or most recently updated.

You do not need to do nesting necessarily. To simply know, which country has most number of cities, just use group by:

select country_id, count(1)
from city
group by country_id

This will give you the number of cities in each country. Then you could use a CTE to get the country with the largest number of cities.

SQL SORTING and FILTERING on HR: Display the country ID and , SQL SORTING and FILTERING on HR Database: Exercise-25 with Solution. 25. Write a query in SQL to display the country ID and number of cities in in SQL to display job ID for those jobs that were done by two or more for� List of the most populous country subdivisions Matrix of country subdivisions List of political and geographic subdivisions by total area , comparing continents, countries, and first-level administrative country subdivisions.

You need to GROUP BY if you want to use aggregate functions.

Given the fact that you're very new to this I think you'll get a lot more out of this if you spend a few minutes reading up on some documentation. Don't worry, this is easy stuff so you'll understand this in no time. Please have a look at the following basic info (MySQL GROUP BY basic info) regarding the use of GROUP BY in MySQL. Your questions are answered in the topic regarding 'MySQL GROUP BY with aggregate functions'.

Basic group by:

SELECT 
    status, COUNT(*)
FROM
    orders
GROUP BY status;

Group by using a join:

SELECT 
    status, SUM(quantityOrdered * priceEach) AS amount
FROM
    orders
        INNER JOIN
    orderdetails USING (orderNumber)
GROUP BY status;

SQL JOINS on HR: Display the country name, city, and number of , SQL JOINS on HR Database: Exercise-21 with Solution. 21. Write a query in SQL to display the country name, city, and number of those� Raleigh has been in the top 10 cities for big data jobs for a while, but it showed the most growth in hiring over the last year. The demand is being fueled by healthcare IT and high-tech research facilities. The area is also home to campuses for Citrix, Lenovo, Cisco, and others. Boston, MA

SELECT x.country 
  FROM country x
  JOIN city y
    ON y.country_id = x.country_id
 GROUP
    BY x.country
 ORDER 
    BY COUNT(*) DESC LIMIT 1;

On the (fantastically unlikely) chance that the most civilised countries have equal numbers of cities, you would have to amend this a little.

MySQL quick tutorial - basic SQL queries in MySQL, The source command executes the backup city.sql script. Since the city table has more than four thousand rows, we cannot see them in one screen. mysql> SELECT Name, HeadOfState FROM country WHERE Name� Free database of worldwide cities in text format suitable for any applications requiring a comprehensive list of cities and country code. It is a subset of the paid edition of GeoDataSource World Cities Database Basic, Premium, Gold, Platinum, Titanium Edition.

What makes this difficult is possible ties, i.e. two or more countries sharing the maximum number of cities. As of MySQL 8 you can use window functions to help you with this. Here I compare the country counts and their maximum and then pick the rows were the two match.

select *
from country
where (country_id, true) in -- true means it is a maximum city country
(
  select country_id, count(*) = max(count(*)) over()
  from city
  group by country_id
);

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[PDF] 7. SQL – Data Handling 7.1 The Query Language SQL expressions, Example: Find countries having cities with a population of 5,000,000 and more; list also city names and Province name and population. J-Tab(Country.code,. Summary: in this tutorial, you will learn how to use the SQL COUNT function to get the number of rows in a specified table.. Introduction to SQL COUNT function. The COUNT() function returns the number of rows in a group.

Comments
  • Thank you, this one helped because I can associate the country with count of cities. And I modified * to country and it limited the result to just country and cities, which helps me visual see everything.
  • Maybe you could, but why would you?
  • Using COUNT(1) can be trouble it might be implemented different between databases optimizers, your better off using COUNT(country_id)
  • Because the questioner wants to know the country with the highest cities! And isn't CTE a neat little way to keep your queries organized and understandable?
  • I don't see why COUNT(1) should be worse than COUNT(country_id) here. Both instruct the DBMS to do unnecessary work (check for each row whether the expression is not null), when you merely want count(*), i.e. count rows.