w3resource

SQL Exercise: Find the referees managed the number of matches

SQL soccer Database: Joins Exercise-51 with Solution

51. From the following tables, write a SQL query to find the number of matches managed by each referee. Return referee name, country 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
       10 | G          | 2016-06-14 | WIN     | N          | 0-2        |    20004 |      70005 |   55408 |       160244 |        63 |       189
       11 | G          | 2016-06-14 | WIN     | N          | 0-2        |    20001 |      70018 |   34424 |       160197 |        61 |       305
       12 | G          | 2016-06-15 | DRAW    | N          | 1-1        |    20009 |      70004 |   38742 |       160320 |        15 |       284
       13 | G          | 2016-06-15 | WIN     | N          | 1-2        |    20003 |      70001 |   38989 |       160405 |        62 |       189
       14 | G          | 2016-06-15 | DRAW    | N          | 1-1        |    20007 |      70015 |   43576 |       160477 |        74 |       206
       15 | G          | 2016-06-16 | WIN     | N          | 2-0        |    20005 |      70013 |   63670 |       160154 |        71 |       374
       16 | G          | 2016-06-16 | WIN     | N          | 2-1        |    20002 |      70003 |   34033 |       160540 |        62 |       212
       17 | G          | 2016-06-16 | WIN     | N          | 0-2        |    20004 |      70016 |   51043 |       160262 |         7 |       411
       18 | G          | 2016-06-17 | DRAW    | N          | 0-0        |    20008 |      70008 |   73648 |       160165 |         6 |       208
       19 | G          | 2016-06-17 | WIN     | N          | 1-0        |    20010 |      70007 |   29600 |       160248 |         2 |       264
       20 | G          | 2016-06-17 | DRAW    | N          | 2-2        |    20009 |      70005 |   38376 |       160086 |        71 |       280
       21 | G          | 2016-06-18 | WIN     | N          | 3-0        |    20006 |      70010 |   33409 |       160429 |        84 |       120
       22 | G          | 2016-06-18 | WIN     | N          | 3-0        |    20001 |      70004 |   39493 |       160064 |        11 |       180
       23 | G          | 2016-06-18 | DRAW    | N          | 1-1        |    20005 |      70015 |   60842 |       160230 |        61 |       280
       24 | G          | 2016-06-19 | DRAW    | N          | 0-0        |    20007 |      70011 |   44291 |       160314 |         3 |       200
       25 | G          | 2016-06-20 | WIN     | N          | 0-1        |    20004 |      70016 |   49752 |       160005 |       125 |       328
       26 | G          | 2016-06-20 | DRAW    | N          | 0-0        |    20003 |      70001 |   45616 |       160463 |        60 |       122
       27 | G          | 2016-06-21 | WIN     | N          | 0-3        |    20010 |      70006 |   28840 |       160544 |        62 |       119
       28 | G          | 2016-06-21 | DRAW    | N          | 0-0        |    20009 |      70012 |   39051 |       160392 |        62 |       301
       29 | G          | 2016-06-21 | WIN     | N          | 0-1        |    20005 |      70017 |   58874 |       160520 |        29 |       244
       30 | G          | 2016-06-21 | WIN     | N          | 0-1        |    20007 |      70018 |   44125 |       160177 |        21 |       195
       31 | G          | 2016-06-22 | WIN     | N          | 0-2        |    20002 |      70013 |   32836 |       160504 |        60 |       300
       32 | G          | 2016-06-22 | WIN     | N          | 2-1        |    20001 |      70008 |   37245 |       160085 |        70 |       282
       33 | G          | 2016-06-22 | WIN     | N          | 2-1        |    20008 |      70009 |   68714 |       160220 |         7 |       244
       34 | G          | 2016-06-22 | DRAW    | N          | 3-3        |    20004 |      70002 |   55514 |       160322 |        70 |       185
       35 | G          | 2016-06-23 | WIN     | N          | 0-1        |    20003 |      70014 |   44268 |       160333 |        79 |       221
       36 | G          | 2016-06-23 | WIN     | N          | 0-1        |    20006 |      70003 |   34011 |       160062 |        63 |       195
       37 | R          | 2016-06-25 | WIN     | P          | 1-1        |    20009 |      70005 |   38842 |       160476 |       126 |       243
       38 | R          | 2016-06-25 | WIN     | N          | 1-0        |    20007 |      70002 |   44342 |       160547 |         5 |       245
       39 | R          | 2016-06-26 | WIN     | N          | 0-1        |    20002 |      70012 |   33523 |       160316 |        61 |       198
       40 | R          | 2016-06-26 | WIN     | N          | 2-1        |    20004 |      70011 |   56279 |       160160 |       238 |       203
       41 | R          | 2016-06-26 | WIN     | N          | 3-0        |    20003 |      70009 |   44312 |       160173 |        62 |       124
       42 | R          | 2016-06-27 | WIN     | N          | 0-4        |    20010 |      70010 |   28921 |       160062 |         3 |       133
       43 | R          | 2016-06-27 | WIN     | N          | 2-0        |    20008 |      70004 |   76165 |       160235 |        63 |       243
       44 | R          | 2016-06-28 | WIN     | N          | 1-2        |    20006 |      70001 |   33901 |       160217 |         5 |       199
       45 | Q          | 2016-07-01 | WIN     | P          | 1-1        |    20005 |      70003 |   62940 |       160316 |        58 |       181
       46 | Q          | 2016-07-02 | WIN     | N          | 3-1        |    20003 |      70001 |   45936 |       160550 |        14 |       182
       47 | Q          | 2016-07-03 | WIN     | P          | 1-1        |    20001 |      70007 |   38764 |       160163 |        63 |       181
       48 | Q          | 2016-07-04 | WIN     | N          | 5-2        |    20008 |      70008 |   76833 |       160159 |        16 |       125
       49 | S          | 2016-07-07 | WIN     | N          | 2-0        |    20004 |      70006 |   55679 |       160322 |         2 |       181
       50 | S          | 2016-07-08 | WIN     | N          | 2-0        |    20005 |      70011 |   64078 |       160160 |       126 |       275
       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
      70010 | Milorad Mazic           |       1227
      70011 | Nicola Rizzoli          |       1211
      70012 | Carlos Velasco Carballo |       1219
      70013 | William Collum          |       1228
      70014 | Ovidiu Hategan          |       1216
      70015 | Sergei Karasev          |       1217
      70016 | Pavel Kralovec          |       1205
      70017 | Svein Oddvar Moen       |       1229
      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
       1210 | ISL          | Iceland
       1211 | ITA          | Italy
       1212 | NIR          | Northern Ireland
       1213 | POL          | Poland
       1214 | POR          | Portugal
       1215 | IRL          | Republic of Ireland
       1216 | ROU          | Romania
       1217 | RUS          | Russia
       1218 | SVK          | Slovakia
       1219 | ESP          | Spain
       1220 | SWE          | Sweden
       1221 | SUI          | Switzerland
       1222 | TUR          | Turkey
       1223 | UKR          | Ukraine
       1224 | WAL          | Wales
       1225 | SLO          | Slovenia
       1226 | NED          | Netherlands
       1227 | SRB          | Serbia
       1228 | SCO          | Scotland
       1229 | NOR          | Norway

Sample Solution:

SQL Code:

-- Selecting the referee name, country name, and the count of matches for each referee in each country
SELECT 
    c.referee_name, -- Selecting the referee name
    b.country_name, -- Selecting the country name
    COUNT(a.match_no) -- Counting the number of matches for each referee in each country
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 
    c.referee_name, -- Grouping the results by referee name -- Grouping the results by country name
    b.country_name; 

Sample Output:

      referee_name       |  country_name  | count
-------------------------+----------------+-------
 Damir Skomina           | Slovenia       |     4
 Martin Atkinson         | England        |     3
 Clement Turpin          | France         |     2
 Jonas Eriksson          | Sweden         |     3
 Ovidiu Hategan          | Romania        |     2
 Sergei Karasev          | Russia         |     2
 Cuneyt Cakir            | Turkey         |     3
 Felix Brych             | Germany        |     3
 Viktor Kassai           | Hungary        |     3
 Carlos Velasco Carballo | Spain          |     3
 Svein Oddvar Moen       | Norway         |     2
 Milorad Mazic           | Serbia         |     3
 Szymon Marciniak        | Poland         |     3
 Bjorn Kuipers           | Netherlands    |     3
 William Collum          | Scotland       |     2
 Mark Clattenburg        | England        |     4
 Nicola Rizzoli          | Italy          |     4
 Pavel Kralovec          | Czech Republic |     2
(18 rows)

Code Explanation:

The given query in SQL that selects the name of referees, the name of countries, and the count of match numbers in the match_mast table for each combination of referee and country.
The JOIN clause in this query then joins the match_mast and referee_mast tables based on the referee_id column and joins the results with soccer_country tables based on the country_id column.
The query groups the results by referee name and country name using the GROUP BY clause and applies an aggregate function, count(), to count the number of match numbers for each combination of referee and country.

Alternative Solution:

Using Subqueries:

-- Selecting the referee name, country name, and the count of matches for each referee in each country
SELECT 
    c.referee_name, -- Selecting the referee name
    b.country_name, -- Selecting the country name
    match_count -- Selecting the count of matches for each referee in each country
FROM 
    referee_mast c -- Specifying the referee_mast table with alias 'c'
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 
    ( -- Subquery to calculate the count of matches for each referee in each country
        SELECT 
            a.referee_id, -- Selecting the referee ID
            b.country_id, -- Selecting the country ID
            COUNT(a.match_no) as match_count -- Counting the number of matches for each referee in each country
        FROM 
            match_mast a -- Specifying the match_mast table with alias 'a'
        JOIN 
            referee_mast b ON a.referee_id = b.referee_id -- Joining the match_mast table with the referee_mast table based on referee ID
        GROUP BY 
            a.referee_id, -- Grouping the results by referee ID
            b.country_id -- Grouping the results by country ID
			-- Joining the main query with the subquery based on referee ID and country ID
    ) a ON a.referee_id = c.referee_id AND a.country_id = b.country_id; 

Explanation:

This query we first perform the join between match_mast and referee_mast on referee_id. Then, in the subquery, we group the results by referee_id and country_id to get the match counts. Finally, we join this subquery with referee_mast and soccer_country to get the referee names and country names.

Relational Algebra Expression:

Relational Algebra Expression: Find the referees managed the number of matches.

Relational Algebra Tree:

Relational Algebra Tree: Find the referees managed the number of matches.

Practice Online


Sample Database: soccer

soccer database relationship structure

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous SQL Exercise: Identify countries where referees managed most matches.
Next SQL Exercise: Find those referees who managed most of the match.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Follow us on Facebook and Twitter for latest update.