SQL Exercise: Find the referees who booked most number of players

SQL soccer Database: Joins Exercise-55 with Solution

55. From the following tables, write a SQL query to find those referees who booked the most number of players. Return referee name, number of matches.

Sample table: player_booked

Sample table: match_mast

Sample table: referee_mast

Sample Solution:

SQL Code:

SELECT c.referee_name,
       count(b.match_no)
FROM player_booked a
JOIN match_mast b ON a.match_no=b.match_no
JOIN referee_mast c ON b.referee_id=c.referee_id
GROUP BY referee_name
HAVING count(b.match_no)=
  (SELECT max(mm)
   FROM
     (SELECT count(b.match_no) mm
      FROM player_booked a
      JOIN match_mast b ON a.match_no=b.match_no
      JOIN referee_mast c ON b.referee_id=c.referee_id
      GROUP BY referee_name) hh);

Sample Output:

   referee_name   | count
------------------+-------
 Mark Clattenburg |    21
(1 row)

Code Explanation:

The provided query in SQL query that retrieves player_booked table aliased as a, match_mast table aliased as b, and referee_mast table aliased as c and returns the name of the referee(s) who received the maximum number of bookings.
The JOIN keyword joins the player_booked and match_mast tables based on the match_no column, the match_mast and the referee_mast tables based on the referee_id column.
The GROUP BY statement groups the results by referee_name.
The HAVING clause filters the results to only include referees who received the maximum number of bookings.
The subquery within the HAVING clause selects the maximum number of bookings from the group of referees.
The query returns the name(s) of the referee(s) who received the maximum number of bookings.

Practice Online

Sample Database: soccer

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