season based database schema/design - sql-server

Question

I have a simple schema for a sports registration system till the concept of a season is introduced:
A player registers as part of a Team
A Team registers as part of a Club
A team plays in a Division
An Organization creates Divisions
This happens every season. So I need a way to keep track of all of this every season. What would be the best approach here? Should I introduce a "Season" entity and make many-to-many relationships between all the entities above as applicable? Or is there a way to just "Archive" everything every season but also be able to pull all the season based data up on the fly (for reporting and what not)?

Answer 1

This design allows teams to move to a different division from season to season, while not having to be re-created every year (though it doesn't allow for things like the Winnipeg Jets moving to Phoenix and keeping their old name with their historical season stats).
CREATE TABLE dbo.Organizations
(
OrgID INT PRIMARY KEY,
Name NVARCHAR(255) NOT NULL UNIQUE
-- , ... other columns
);
CREATE TABLE dbo.Divisions
(
DivisionID INT PRIMARY KEY,
Name NVARCHAR(255) NOT NULL,
OrgID INT NOT NULL FOREIGN KEY REFERENCES dbo.Organizations(OrgID)
-- , ... other columns
-- UNIQUE might be (Name) or (OrgID, Name)
);
CREATE TABLE dbo.Clubs
(
ClubID INT PRIMARY KEY,
Name NVARCHAR(255) NOT NULL UNIQUE,
-- , ... other columns
);
CREATE TABLE dbo.Teams
(
TeamID INT PRIMARY KEY,
Name NVARCHAR(255) NOT NULL,
ClubID INT NOT NULL FOREIGN KEY REFERENCES dbo.Clubs(ClubID)
-- , ... other columns
);
Now to keep track of seasons:
CREATE TABLE dbo.Seasons
(
SeasonID INT PRIMARY KEY,
StartDate DATE NOT NULL,
EndDate DATE,
Name NVARCHAR(255) NOT NULL -- e.g. '1997-98' for seasons that cross Jan 1
-- , ... other columns
);
CREATE TABLE dbo.SeasonTeams
(
SeasonID INT FOREIGN KEY REFERENCES dbo.Seasons(SeasonID),
DivisionID INT FOREIGN KEY REFERENCES dbo.Divisions(DivisionID),
TeamID INT FOREIGN KEY REFERENCES dbo.Teams(TeamID),
PRIMARY KEY (SeasonID, DivisionID, TeamID)
);
You probably want constraints or triggers to prevent a team from belonging to more than one division in any given year.
Now you'll also want to denote a roster for a given season / team.
CREATE TABLE dbo.Players
(
PlayerID INT PRIMARY KEY,
Name NVARCHAR(255) NOT NULL,
-- , ... other columns
);
CREATE TABLE dbo.TeamRoster
(
PlayerID INT NOT NULL FOREIGN KEY REFERENCES dbo.Players(PlayerID),
TeamID INT NOT NULL,
SeasonID INT NOT NULL,
DivisionID INT NOT NULL,
FOREIGN KEY (TeamID, SeasonID, DivisionID) REFERENCES
dbo.SeasonTeams (TeamID, SeasonID, DivisionID)
);
You'll also want tables for schedules, standings, player stats etc... but that should be a start.