SQL Exercise: Number of matches played at each venue and their city
14. From the following tables, write a SQL query to count the number of matches played at each venue. Sort the result-set on venue name. Return Venue name, city, and number of matches.
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 table: soccer_city
city_id | city | country_id ---------+---------------+------------ 10001 | Paris | 1207 10002 | Saint-Denis | 1207 10003 | Bordeaux | 1207 10004 | Lens | 1207 10005 | Lille | 1207 10006 | Lyon | 1207 10007 | Marseille | 1207 10008 | Nice | 1207 10009 | Saint-Etienne | 1207 10010 | Toulouse | 1207Sample 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 Solution:
SQL Code:
-- Selecting venue_name, city, and the count of matches for each venue
SELECT a.venue_name, b.city, COUNT(c.match_no)
-- From clause with JOINs between soccer_venue, soccer_city, and match_mast
FROM soccer_venue a
JOIN soccer_city b ON a.city_id = b.city_id
JOIN match_mast c ON a.venue_id = c.venue_id
-- Grouping the results by venue_name and city to count matches for each venue
GROUP BY venue_name, city
-- Ordering the results by venue_name
ORDER BY venue_name;
Sample Output:
venue_name | city | count
-------------------------+---------------+-------
Parc des Princes | Paris | 5
Stade Bollaert-Delelis | Lens | 4
Stade de Bordeaux | Bordeaux | 5
Stade de France | Saint-Denis | 7
Stade de Lyon | Lyon | 6
Stade de Nice | Nice | 4
Stade Geoffroy Guichard | Saint-Etienne | 4
Stade Pierre Mauroy | Lille | 6
Stade VElodrome | Marseille | 6
Stadium de Toulouse | Toulouse | 4
(10 rows)
Code Explanation:
The said query in SQL that selects the venue name, city, and count of matches played in each venue and city combination, by joining tables soccer_venue, soccer_city, and match_mast on the venue_id and city_id fields.
The result is grouped by venue_name and city, and ordered by venue_name in ascending order.
Alternative Solutions:
Using Subquery with Aggregation:
-- Selecting venue_name, city, and the count of matches for each venue using a subquery
SELECT a.venue_name, b.city,
-- Subquery to count the number of matches for each venue
(SELECT COUNT(*)
-- From clause within the subquery to select from match_mast (aliased as c)
FROM match_mast c
-- Condition for joining match_mast based on venue_id
WHERE a.venue_id = c.venue_id) as match_count
-- From clause with JOIN between soccer_venue and soccer_city using city_id
FROM soccer_venue a
JOIN soccer_city b ON a.city_id = b.city_id
-- Ordering the results by venue_name
ORDER BY a.venue_name;
Explanation:
This query uses a subquery in the select clause to calculate the count of matches for each venue. It correlates the subquery with the outer query using the venue_id. The subquery counts the number of matches for each venue, and the result is selected alongside the venue name and city.
Using a Correlated Subquery in the JOIN:
-- Selecting venue_name, city, and the count of matches for each venue using LEFT JOIN
SELECT a.venue_name, b.city, COUNT(c.match_no)
-- From clause with JOINs between soccer_venue, soccer_city, and match_mast (using LEFT JOIN)
FROM soccer_venue a
JOIN soccer_city b ON a.city_id = b.city_id
LEFT JOIN match_mast c ON a.venue_id = c.venue_id
-- Grouping the results by venue_name and city to count matches for each venue
GROUP BY a.venue_name, b.city
-- Ordering the results by venue_name
ORDER BY a.venue_name;
Explanation:
This query uses a correlated subquery within the JOIN clause. It joins all venues with their respective matches, and then groups the results by venue name and city. This ensures that each venue is counted only once.
Using a Subquery in the FROM Clause:
-- Selecting venue_name, city, and the count of matches for each venue using LEFT JOIN and COALESCE
SELECT a.venue_name, b.city, COALESCE(match_count, 0) as match_count
-- From clause with JOINs between soccer_venue, soccer_city, and a subquery (aliased as c) with LEFT JOIN
FROM soccer_venue a
JOIN soccer_city b ON a.city_id = b.city_id
LEFT JOIN (
-- Subquery to count the number of matches for each venue
SELECT venue_id, COUNT(match_no) as match_count
-- From clause to select from match_mast
FROM match_mast
-- Grouping the results by venue_id to count matches for each venue
GROUP BY venue_id
) c ON a.venue_id = c.venue_id
-- Ordering the results by venue_name
ORDER BY a.venue_name;
Explanation:
This query uses a subquery in the FROM clause to calculate the match counts for each venue. It then performs a LEFT JOIN with the venues table, ensuring that all venues are included in the result, even if they have no matches. The COALESCE function is used to handle cases where there are no matches.
Relational Algebra Expression:
Relational Algebra Tree:
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Sample Database: soccer
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