# ERD Relationiships

Can someone please verify if i have the ERD correct - Any suggestions or opinons are greatly appreciated.

1.     The five entities identified are SoccerGame, Field, Team, Player, Referee, SoccerGameRule.
2.     Here are the relationships:
Each SoccerGame is played on one and only one Field; each Field hosts zero, one or more SoccerGame.
Each Field has zero, one or more FieldFeature; each FieldFeature is part of one and only one Field.
Each Attribute can participate in zero, one or more FieldFeature; each FieldFeature has one and only one Field.
Each Team has eleven and only eleven players; each Player is part of one and only one Team.
Each SoccerGame has one and only one Referree; each Referree arbiters zero, one or more SoccerGames.
Each SoccerGame has one and only one (Home) Team; each (Home) Team is part of zero, one or more SoccerGames.
Each SoccerGame has one and only one (Away) Team; each (Away)Team is part of zero, one or more SoccerGames.
3.     Further define relationships with cardinalities – Interesting to note is that a team can have exactly 11 players, and soccer game can have exactly two playing teams and one referee.
4.     select Primary Keys – see selected Primary Keys on the Figure 1 below. They are self-explanatory.
5.     determine Foreign Keys – see selected Foreign Keys on the Figure 1 below. . They are self-explanatory.

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Commented:
I'm not sure about these 2:
Each Field has zero, one or more FieldFeature; each FieldFeature is part of one and only one Field.
Each Attribute can participate in zero, one or more FieldFeature; each FieldFeature has one and only one Field.

Depends on what is in the FieldFeature table and the Attribute table. Also, thes tables are not mentioned under 1.

Furthermore: A team normally has 16 players, 11 on the field plus 5 extra players, that can play part of the game. And there are 3 referees, one on the field and 2 on the sideline.

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Author Commented:
Good points Dready.. I am not a soccer player but a friend of mine had me compile this.. :) I am going to have further look into your suggestions.. Good points.. thanks so much for replying so fast
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Commented:
This is an interesting question. It's been a while since I have seen a conceptual question.

In any event, by my understanding your going to need about 7-8 entities. Note the following points.

1) For the SoccerGame: You would need an associative entity between SoccerGame and Team because you don't want to put the Home team and away team in one record where someone could mistakenly put a team as home and away. Call the associative entity "GameTeams" or something. It will look as follows:

GAMETEAMS
---------------
Autonumber
SoccerGamePK (FK)(PK)
TeamPK (FK)(PK)
HomeAway(PK)

With the above, you would be able to enter the same team as home as away. Of course, GAMETEAMS autonumber will have to be a foreign key in SoccerGame

2) As dready noted, the "Each Field has zero, one or more FieldFeature..." and "Each Attribute can participate in zero, one or more FieldFeature..." if off. With this, you would need to add two more entities, FieldFeature & Attributes

I didn't see the figure you were referring to but the final breakdown as I see it is as follows:

SOCCERGAME
-----------------
Autonum (PK)
FieldPK (FK)
GameTeamsAutoNum (FK)
RefereePK (FK)

GAMETEAMS
---------------
Autonumber
SoccerGamePK (FK)(PK)
TeamPK (FK)(PK)
HomeAway(PK)

TEAM
-------
Autonum (PK)

TEAMPLAYERS
-----------------
Autonum
TeamPK (FK)
PlayerPK (FK)

PLAYER
---------
Autonum (PK)

FIELD
-------
Autonum (PK)
FieldFeaturePK (FK)

FIELDFEATURE
------------------
Autonum (PK)
AttributePK (FK)

ATTRIBUTE
-------------
Autonum (PK)

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