How to properly organize historical data in the same table? - mysql

Question

Main organization and problem
I'm working on a database of football matches, this db is organized in the following structure:
Country -> Competition -> Season -> Data
The basic matter of the question is that I'm not pretty sure that my database schema is correct.
Explain the data structure
The main "problem" is that each Data is grouped by a specific season, let's take in consideration the country England:
Country | Competition | Season |
England | Premier League | 2017/2018 |
England | Premier League | 2016/2017 |
England | Premier League | 2015/2016 |
England | Premier League | 2014/2015 |
England | Premier League | 2013/2014 |
as you can see the England have a competition named Premier League which is divided into 5 seasons.
Each competition is divided into rounds, a competition can be formed by a single round, but also by more rounds.
Each round could be divided into groups, this depends on the type of competition, some competitions aren't divided into groups.
Database structure
Based on my explaination of data relationship, I configured a database structure which have the following table:
country: contains all the countries informations available.
competition: contains all the competitions details.
competition_seasons: contains all the competition seasons.
competition_rounds: contains all the rounds available for the competition.
competition_groups: contains all the groups available for the competition.
league_ranking: contains all the ranking position of each team that partecipate on the specific competition.
The database schema is this (I does not have enough rep to display the image you need click on the link):
enter image description here
Database code
-- -----------------------------------------------------
-- Table `mydb`.`country`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`country` (
`id` INT NOT NULL,
`name` VARCHAR(255) NOT NULL,
`link` VARCHAR(255) NOT NULL,
`iso` VARCHAR(45) NOT NULL,
PRIMARY KEY (`id`))
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`competition`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`competition` (
`id` INT NOT NULL,
`country_id` INT NOT NULL,
`name` VARCHAR(255) NOT NULL,
`link` VARCHAR(255) NOT NULL,
PRIMARY KEY (`id`),
INDEX `id_idx` (`country_id` ASC),
CONSTRAINT `FK_country_competition_country_id`
FOREIGN KEY (`country_id`)
REFERENCES `mydb`.`country` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`competition_seasons`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`competition_seasons` (
`season_id` INT NOT NULL,
`competition_id` INT NOT NULL,
`name` VARCHAR(255) NOT NULL,
`create_at` DATETIME NULL,
`update_at` DATETIME NULL,
INDEX `competition_id_idx` (`competition_id` ASC),
PRIMARY KEY (`season_id`),
CONSTRAINT `FK_competition_competition_seasons_competition_id`
FOREIGN KEY (`competition_id`)
REFERENCES `mydb`.`competition` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`competition_groups`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`competition_groups` (
`group_id` INT NOT NULL,
`competition_id` INT NOT NULL,
`round_id` INT NOT NULL,
INDEX `group_id_idx` (`group_id` ASC),
INDEX `competition_id_idx` (`competition_id` ASC),
INDEX `round_id_idx` (`round_id` ASC),
CONSTRAINT `FK_group_competition_groups_group_id`
FOREIGN KEY (`group_id`)
REFERENCES `mydb`.`group` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `FK_competition_competition_groups_competition_id`
FOREIGN KEY (`competition_id`)
REFERENCES `mydb`.`competition` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `FK_round_competition_groups_round_id`
FOREIGN KEY (`round_id`)
REFERENCES `mydb`.`round` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`competition_rounds`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`competition_rounds` (
`competition_id` INT NOT NULL,
`round_id` INT NOT NULL,
INDEX `competition_id_idx` (`competition_id` ASC),
INDEX `round_id_idx` (`round_id` ASC),
CONSTRAINT `FK_competition_competition_rounds_competition_id`
FOREIGN KEY (`competition_id`)
REFERENCES `mydb`.`competition` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `FK_round_competition_rounds_round_id`
FOREIGN KEY (`round_id`)
REFERENCES `mydb`.`round` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `mydb`.`league_ranking`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `mydb`.`league_ranking` (
`id` INT NOT NULL,
`position` INT NULL,
`team_id` INT NULL,
`season_id` INT NULL,
`round_id` INT NULL,
`competition_id` INT NULL,
`group_id` INT NULL,
`played_matches` INT NULL,
`wins` INT NULL,
`draws` INT NULL,
`losses` INT NULL,
`goals_for` INT NULL,
`goals_against` INT NULL,
`goals_difference` INT NULL,
`points` INT NULL,
PRIMARY KEY (`id`),
CONSTRAINT `FK_team_league_ranking_teamd_id`
FOREIGN KEY (`id`)
REFERENCES `mydb`.`team` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `FK_round_league_ranking_round_id`
FOREIGN KEY (`id`)
REFERENCES `mydb`.`round` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `FK_competition_league_ranking_competition_id`
FOREIGN KEY (`id`)
REFERENCES `mydb`.`competition` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `FK_group_league_ranking_group_id`
FOREIGN KEY (`id`)
REFERENCES `mydb`.`group` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
is my database schema correct for store historical season?

Answer 1

Assuming
A competition is composed of 1 or more rounds,
A round is optionally composed of 1 or more groups.
Then I recommend
One table containing one row per 'competition'.
One table containing one row per 'round'. It should contain a competition_id that is a FK to competition.id.
One table containing one row per 'group'. It should contain a round_id that is a FK to round.id.
(Etc.)
Those are examples of doing "1:many" mappings. (Note "0 or more" and "optionally" are merely edge cases of "1:many", and do not require extra effort.)
I say "one table" because "vertical splitting" is rarely unnecessary. Simply put all the attributes for a "competition" in a single table. When some attribute (such as the 'rounds') is repeated, then it cannot be put in the same table.
(The table name competition_rounds, though descriptive, was confusing me.)
A related question... Are all the 'rounds' of a 'competition' played in a single country? I see country_id in competition; I wonder if it should be moved to rounds?

Answer 2

#1. First of all, I didn't understand the usages of "competition_round" table, here you defined this table with two column "competition_id" and "round_id". Anyway, you have defined "competition_id" and "round_id" in "leage_ranking" table, so, I suggest not to use the extra table to store the same data again.
#2. As you mentioned you want to store the data historically, then I am assuming there will be less transaction or not might be. So, I suggest you de-normalize the table. Because the end of the day you are going to analyze the data and going to perform lots of data mining on historical data to provide appropriate business expectations.
#3. Other than this it seems a good data model, as per my experience.
Refer this link for understanding the database design patterns