ER diagram: cricket tournament

An ER diagram models the entities, attributes and relationships of the tournament. The assumptions below follow the usual cricket set-up.

Entities and attributes

• Tournament (t_id, name): the competition.
• Team (team_id, name): about 10 teams take part in one tournament.
• Match (match_no, date): played between two teams.
• Referee (ref_id, name): each match has 3 referees.
• Ground (ground_id, name, seat_capacity, size): each match is played on one ground.
• Member (role, experience) and Player (run_scored, wicket_taken): ISA specializations of Team, as drawn in the given solution (a team is made up of players and other members such as the coach or manager).

Relationships

• Team participates in Tournament: N : 1 (10 teams to 1 tournament).
• Team plays Match: M : N (exactly 2 teams per match).
• Match has Referee: 1 : 3.
• Match played on Ground: N : 1.
• Player and Member are subclasses (ISA) of Team.

ER diagram

              [Tournament]
                   | 1
             <participates>
                   | N
                 [Team]-----2-----<plays>
                   |                 | N
                  ISA                |
                 /   \               |
          [Member]   [Player]        |
                                     |
 [Referee]--3----<has>----1-------[Match]--N--<played_on>--1--[Ground]
                                   (date)            (seat_capacity, size)

 Member: role, experience     Player: run_scored, wicket_taken

In the diagram, rectangles are entities, diamonds (shown as <...>) are relationships, and the ISA triangle shows that Member and Player inherit the attributes of the superclass. Each number is written next to the entity it counts: for example, 3 referees per match, 2 teams per match and 10 (N) teams per tournament.