SQL Exercise: Find the yellow cards received by each country

SQL soccer Database: Joins Exercise-17 with Solution

17. From the following tables, write a SQL query to count the number of yellow cards each country has received. Return country name and number of yellow cards.

Sample table: soccer_country

Sample table: player_booked

Sample Solution:

SQL Code:

SELECT country_name, COUNT(*)
FROM soccer_country 
JOIN player_booked
ON soccer_country.country_id=player_booked.team_id
GROUP BY country_name
ORDER BY COUNT(*) DESC;

Sample Output:

    country_name     | count
---------------------+-------
 Italy               |    16
 France              |    13
 Portugal            |    13
 Hungary             |    12
 Iceland             |    12
 Wales               |    11
 Germany             |    11
 Romania             |    10
 Albania             |    10
 Poland              |    10
 Republic of Ireland |     9
 Slovakia            |     9
 Belgium             |     9
 Croatia             |     8
 Turkey              |     7
 Austria             |     7
 Northern Ireland    |     6
 Czech Republic      |     5
 Spain               |     5
 Ukraine             |     5
 Switzerland         |     5
 England             |     3
 Sweden              |     3
 Russia              |     2
(24 rows)

Code Explanation:

The said query in SQL that selects a list of all countries along with the count of player bookings for each country from the tables 'soccer_country' and 'player_booked'.
The JOIN keyword with ON clause is used to specify the join condition where the country ID from the 'soccer_country' table matches the team ID from the 'player_booked' table.
The GROUP BY clause groups the results by country name. This means that the COUNT(*) function will count the number of player bookings for each country.
The query is using the ORDER BY clause to sort the results in descending order based on the count of player bookings.

Relational Algebra Expression:

Relational Algebra Tree:

Practice Online

Sample Database: soccer

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