SQL Exercise: Find the number of matches each referee managed
53. From the following tables, write a SQL query to find those referees who managed the number of matches at each venue. Return referee name, country name, venue name, number of matches.
Sample table: match_mast
match_no | play_stage | play_date | results | decided_by | goal_score | venue_id | referee_id | audence | plr_of_match | stop1_sec | stop2_sec
----------+------------+------------+---------+------------+------------+----------+------------+---------+--------------+-----------+-----------
1 | G | 2016-06-11 | WIN | N | 2-1 | 20008 | 70007 | 75113 | 160154 | 131 | 242
2 | G | 2016-06-11 | WIN | N | 0-1 | 20002 | 70012 | 33805 | 160476 | 61 | 182
3 | G | 2016-06-11 | WIN | N | 2-1 | 20001 | 70017 | 37831 | 160540 | 64 | 268
4 | G | 2016-06-12 | DRAW | N | 1-1 | 20005 | 70011 | 62343 | 160128 | 0 | 185
5 | G | 2016-06-12 | WIN | N | 0-1 | 20007 | 70006 | 43842 | 160084 | 125 | 325
6 | G | 2016-06-12 | WIN | N | 1-0 | 20006 | 70014 | 33742 | 160291 | 2 | 246
7 | G | 2016-06-13 | WIN | N | 2-0 | 20003 | 70002 | 43035 | 160176 | 89 | 188
8 | G | 2016-06-13 | WIN | N | 1-0 | 20010 | 70009 | 29400 | 160429 | 360 | 182
9 | G | 2016-06-13 | DRAW | N | 1-1 | 20008 | 70010 | 73419 | 160335 | 67 | 194
........
51 | F | 2016-07-11 | WIN | N | 1-0 | 20008 | 70005 | 75868 | 160307 | 161 | 181
Sample table: referee_mast
referee_id | referee_name | country_id
------------+-------------------------+------------
70001 | Damir Skomina | 1225
70002 | Martin Atkinson | 1206
70003 | Felix Brych | 1208
70004 | Cuneyt Cakir | 1222
70005 | Mark Clattenburg | 1206
70006 | Jonas Eriksson | 1220
70007 | Viktor Kassai | 1209
70008 | Bjorn Kuipers | 1226
70009 | Szymon Marciniak | 1213
.......
70018 | Clement Turpin | 1207
Sample table: soccer_country
country_id | country_abbr | country_name
------------+--------------+---------------------
1201 | ALB | Albania
1202 | AUT | Austria
1203 | BEL | Belgium
1204 | CRO | Croatia
1205 | CZE | Czech Republic
1206 | ENG | England
1207 | FRA | France
1208 | GER | Germany
1209 | HUN | Hungary
.......
1229 | NOR | Norway
Sample table: soccer_venue
venue_id | venue_name | city_id | aud_capacity
----------+-------------------------+---------+--------------
20001 | Stade de Bordeaux | 10003 | 42115
20002 | Stade Bollaert-Delelis | 10004 | 38223
20003 | Stade Pierre Mauroy | 10005 | 49822
20004 | Stade de Lyon | 10006 | 58585
20005 | Stade VElodrome | 10007 | 64354
20006 | Stade de Nice | 10008 | 35624
20007 | Parc des Princes | 10001 | 47294
20008 | Stade de France | 10002 | 80100
20009 | Stade Geoffroy Guichard | 10009 | 42000
20010 | Stadium de Toulouse | 10010 | 33150
Sample Solution:
SQL Code:
-- Selecting the referee name, country name, venue name, and match count for each referee, country, and venue
SELECT
c.referee_name, -- Selecting the referee name
b.country_name, -- Selecting the country name
d.venue_name, -- Selecting the venue name
COUNT(a.match_no) -- Counting the number of matches for each combination of referee, country, and venue
FROM
match_mast a -- Specifying the match_mast table with alias 'a'
JOIN
referee_mast c ON a.referee_id = c.referee_id -- Joining the match_mast table with the referee_mast table based on referee ID
JOIN
soccer_country b ON c.country_id = b.country_id -- Joining the referee_mast table with the soccer_country table based on country ID
JOIN
soccer_venue d ON a.venue_id = d.venue_id -- Joining the match_mast table with the soccer_venue table based on venue ID
GROUP BY
c.referee_name, -- Grouping the results by referee name
b.country_name, -- Grouping the results by country name
d.venue_name -- Grouping the results by venue name
-- Sorting the results by referee name
ORDER BY
c.referee_name;
Sample Output:
referee_name | country_name | venue_name | count
-------------------------+----------------+-------------------------+-------
Bjorn Kuipers | Netherlands | Stade de Bordeaux | 1
Bjorn Kuipers | Netherlands | Stade de France | 2
Carlos Velasco Carballo | Spain | Stade Bollaert-Delelis | 2
Carlos Velasco Carballo | Spain | Stade Geoffroy Guichard | 1
Clement Turpin | France | Parc des Princes | 1
Clement Turpin | France | Stade de Bordeaux | 1
Cuneyt Cakir | Turkey | Stade de Bordeaux | 1
Cuneyt Cakir | Turkey | Stade de France | 1
Cuneyt Cakir | Turkey | Stade Geoffroy Guichard | 1
Damir Skomina | Slovenia | Stade de Nice | 1
Damir Skomina | Slovenia | Stade Pierre Mauroy | 3
Felix Brych | Germany | Stade Bollaert-Delelis | 1
Felix Brych | Germany | Stade de Nice | 1
Felix Brych | Germany | Stade VElodrome | 1
Jonas Eriksson | Sweden | Parc des Princes | 1
Jonas Eriksson | Sweden | Stade de Lyon | 1
Jonas Eriksson | Sweden | Stadium de Toulouse | 1
Mark Clattenburg | England | Stade de France | 1
Mark Clattenburg | England | Stade de Lyon | 1
Mark Clattenburg | England | Stade Geoffroy Guichard | 2
Martin Atkinson | England | Parc des Princes | 1
Martin Atkinson | England | Stade de Lyon | 1
Martin Atkinson | England | Stade Pierre Mauroy | 1
Milorad Mazic | Serbia | Stade de France | 1
Milorad Mazic | Serbia | Stade de Nice | 1
Milorad Mazic | Serbia | Stadium de Toulouse | 1
Nicola Rizzoli | Italy | Parc des Princes | 1
Nicola Rizzoli | Italy | Stade de Lyon | 1
Nicola Rizzoli | Italy | Stade VElodrome | 2
Ovidiu Hategan | Romania | Stade de Nice | 1
Ovidiu Hategan | Romania | Stade Pierre Mauroy | 1
Pavel Kralovec | Czech Republic | Stade de Lyon | 2
Sergei Karasev | Russia | Parc des Princes | 1
Sergei Karasev | Russia | Stade VElodrome | 1
Svein Oddvar Moen | Norway | Stade de Bordeaux | 1
Svein Oddvar Moen | Norway | Stade VElodrome | 1
Szymon Marciniak | Poland | Stade de France | 1
Szymon Marciniak | Poland | Stade Pierre Mauroy | 1
Szymon Marciniak | Poland | Stadium de Toulouse | 1
Viktor Kassai | Hungary | Stade de Bordeaux | 1
Viktor Kassai | Hungary | Stade de France | 1
Viktor Kassai | Hungary | Stadium de Toulouse | 1
William Collum | Scotland | Stade Bollaert-Delelis | 1
William Collum | Scotland | Stade VElodrome | 1
(44 rows)
Code Explanation:
The said query in SQL that retrieves data from multiple tables and returns the number of matches each referee has officiated in each venue and country.
The JOIN clause joins the match_mast and referee_mast tables based on the referee_id column, the referee_mast and soccer_country tables based on the country_id column and the match_mast and soccer_venue tables based on the venue_id column.
The GROUP BY statement groups the results by referee_name, country_name, and venue_name.
The ORDER BY statement sorts the results in ascending order by referee_name.
Alternative Solutions:
Subquery with JOINs:
-- Selecting the referee name, country name, venue name, and match count for each referee, country, and venue
SELECT
c.referee_name, -- Selecting the referee name
b.country_name, -- Selecting the country name
d.venue_name, -- Selecting the venue name
match_count -- Selecting the match count
FROM
( -- Subquery to calculate the match count for each combination of referee, country, and venue
SELECT
a.referee_id, -- Selecting the referee ID
c.country_id, -- Selecting the country ID
a.venue_id, -- Selecting the venue ID
COUNT(a.match_no) as match_count -- Counting the number of matches for each combination
FROM
match_mast a -- Specifying the match_mast table with alias 'a'
JOIN
referee_mast c ON a.referee_id = c.referee_id -- Joining the match_mast table with the referee_mast table based on referee ID
JOIN
soccer_country b ON c.country_id = b.country_id -- Joining the referee_mast table with the soccer_country table based on country ID
GROUP BY
a.referee_id, c.country_id, a.venue_id -- Grouping the results by referee ID, country ID, and venue ID
) subquery -- Alias for the subquery
JOIN
referee_mast c ON subquery.referee_id = c.referee_id -- Joining the subquery with the referee_mast table based on referee ID
JOIN
soccer_country b ON subquery.country_id = b.country_id -- Joining the subquery with the soccer_country table based on country ID
JOIN
soccer_venue d ON subquery.venue_id = d.venue_id -- Joining the subquery with the soccer_venue table based on venue ID
-- Sorting the results by referee name
ORDER BY
c.referee_name;
Explanation:
This query first creates a subquery that calculates the match count for each combination of referee, country, and venue. It then joins this subquery with the necessary tables to retrieve the referee name, country name, venue name, and match count.
Using CROSS JOIN and Subquery:
-- Selecting the referee name, country name, venue name, and match count for each referee, country, and venue
SELECT
c.referee_name, -- Selecting the referee name
b.country_name, -- Selecting the country name
d.venue_name, -- Selecting the venue name
COUNT(a.match_no) -- Counting the number of matches
FROM
match_mast a -- Specifying the match_mast table with alias 'a'
CROSS JOIN
referee_mast c -- Performing a cross join with the referee_mast table with alias 'c'
CROSS JOIN
soccer_country b -- Performing a cross join with the soccer_country table with alias 'b'
CROSS JOIN
soccer_venue d -- Performing a cross join with the soccer_venue table with alias 'd'
WHERE
a.referee_id = c.referee_id -- Matching the referee ID between match_mast and referee_mast
AND c.country_id = b.country_id -- Matching the country ID between referee_mast and soccer_country
AND a.venue_id = d.venue_id -- Matching the venue ID between match_mast and soccer_venue
GROUP BY
c.referee_name, b.country_name, d.venue_name -- Grouping the results by referee name, country name, and venue name
-- Sorting the results by referee name
ORDER BY
c.referee_name;
Explanation:
This query uses CROSS JOINs to generate all possible combinations of referees, countries, and venues. It then filters the results to match the respective IDs and groups by referee name, country name, and venue name.
Using a Self-Join and Subquery:
-- Selecting the referee name, country name, venue name, and match count for each referee, country, and venue
SELECT
c.referee_name, -- Selecting the referee name
b.country_name, -- Selecting the country name
d.venue_name, -- Selecting the venue name
COUNT(a.match_no) -- Counting the number of matches
FROM
match_mast a -- Specifying the match_mast table with alias 'a'
JOIN
referee_mast c ON a.referee_id = c.referee_id -- Joining with referee_mast table on referee ID
JOIN
soccer_country b ON c.country_id = b.country_id -- Joining with soccer_country table on country ID
JOIN
soccer_venue d ON a.venue_id = d.venue_id -- Joining with soccer_venue table on venue ID
JOIN
(
-- Subquery to calculate the match count for each referee, country, and venue
SELECT
a.referee_id,
c.country_id,
a.venue_id,
COUNT(a.match_no) as match_count -- Counting the number of matches
FROM
match_mast a -- Specifying the match_mast table with alias 'a'
JOIN
referee_mast c ON a.referee_id = c.referee_id -- Joining with referee_mast table on referee ID
JOIN
soccer_country b ON c.country_id = b.country_id -- Joining with soccer_country table on country ID
GROUP BY
a.referee_id, c.country_id, a.venue_id -- Grouping by referee ID, country ID, and venue ID
) subquery ON a.referee_id = subquery.referee_id -- Joining with the subquery on referee ID
AND c.country_id = subquery.country_id -- Joining with the subquery on country ID
AND a.venue_id = subquery.venue_id -- Joining with the subquery on venue ID
GROUP BY
c.referee_name, b.country_name, d.venue_name -- Grouping the results by referee name, country name, and venue name
-- Sorting the results by referee name
ORDER BY
c.referee_name;
Explanation:
This query first creates a subquery to calculate the match count for each combination of referee, country, and venue. It then joins this subquery with the main query using a self-join on the respective IDs.
Relational Algebra Expression:
Relational Algebra Tree:
PREV : Find those referees who managed most of the match.
NEXT : Find the referees and number of booked he made.
Practice Online
Sample Database: soccer
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