The JOIN operation/ja

game ゲームテーブル 試合日や参加チームなどを記録

  id      試合id
  mdate   試合日
  stadium スタジアム
  team1   チーム１（アルファベット３文字）
  team2   チーム２（アルファベット３文字）



goal ゴールテーブル　ゴールの記録

  matchid 試合id
  teamid  チームid（アルファベット３文字）
  player  プレイヤー
  gtime   ゴール時間



eteam 参加チームテーブル

  id       チームid（アルファベット３文字）
  teamname チーム名前
  coach    コーチ


PK 主キー
FK 外部キー

game

id	mdate	stadium	team1	team2
1001	8 June 2012	National Stadium, Warsaw	POL	GRE
1002	8 June 2012	Stadion Miejski (Wroclaw)	RUS	CZE
1003	12 June 2012	Stadion Miejski (Wroclaw)	GRE	CZE
1004	12 June 2012	National Stadium, Warsaw	POL	RUS
...

goal

matchid	teamid	player	gtime
1001	POL	Robert Lewandowski	17
1001	GRE	Dimitris Salpingidis	51
1002	RUS	Alan Dzagoev	15
1002	RUS	Roman Pavlyuchenko	82
...

eteam

id	teamname	coach
POL	Poland	Franciszek Smuda
RUS	Russia	Dick Advocaat
CZE	Czech Republic	Michal Bilek
GRE	Greece	Fernando Santos
...

JOIN と UEFA EURO 2012

このチュートリアルでは JOIN を紹介します。これで2個かそれ以上のテーブルを扱えるようになります。 ここのテーブルには UEFA EURO 2012 Football Championship in Poland and Ukraine（欧州選手権サッカーチャンピオンシップ イン ポーランド・ウクライナ） の全試合のゴールが格納されています。

mysqlフォーマットのデータはこちらから http://sqlzoo.net/euro2012.sql

サマリー

最初の例としてラストネームが Bender である選手のゴール記録が示されている。

「*」でテーブルの全フィールド（カラム）を宣言する。これは matchid, teamid, player, gtime を短く書く方法である。

matchid と player 名をドイツ(Germany)チームの全ゴールについて表示する。ドイツプレイヤーを識別するには、次を確認: teamid = 'GER'

SELECT * FROM goal 
  WHERE player LIKE '%Bender'

SELECT matchid, player 
 FROM goal
   WHERE teamid LIKE 'GER'

上記のクエリ―では、Lars Benderのゴールは ゲーム 1012 で確認できる。さて、この試合でどのチーム達がプレイしていたか知りたい。

goalテーブルで試合番号は matchid だが、gameテーブルでは id となっていることに注意する。 試合 2012 の情報を知るには game の該当する行を参照する。

試合 1012 の id, stadium, team1, team2 を表示する。

SELECT id,stadium,team1,team2
  FROM game

SELECT id,stadium,team1,team2
 FROM game
WHERE id=1012

JOIN を利用して、２つのステップを組み合わせて単独のクエリ―にすることができる。

gameとgoalの詳細を得るには、

SELECT *
  FROM game JOIN goal ON (id=matchid)

FROM節はgoalテーブルとgameテーブルのデータを統合する。 ON で gameの行と goalの行を、goalテーブルのidをgameの matchidと一致させて対応させる。 (もっと明確に言うとすれば、こう言う。
ON (game.id=goal.matchid)

得点が有るたびに、goalテーブルから playerを表示して、stadium 名は game ゲーブルから表示する。

ドイツの全ゴールについて player, teamid ,stadium, mdate を表示するように修正する。

SELECT player,stadium
  FROM game JOIN goal ON (id=matchid)

SELECT player,teamid,stadium,mdate
  FROM game JOIN goal ON (id=matchid)
 WHERE teamid='GER'

Use the same JOIN as in the previous question.

Show the team1, team2 and player for every goal scored by a player called Mario player LIKE 'Mario%'

SELECT team1, team2, player
  FROM game JOIN goal ON (id=matchid)
WHERE player LIKE 'Mario%'

The table eteam gives details of every national team including the coach. You can JOIN goal to eteam using the phrase goal JOIN eteam on teamid=id

Show player, teamid, coach, gtime for all goals scored in the first 10 minutes gtime<=10

SELECT player, teamid, gtime
  FROM goal 
 WHERE gtime<=10

SELECT player, teamid, coach, gtime
  FROM goal JOIN eteam ON (teamid=id)
 WHERE gtime<=10

To JOIN game with eteam you could use either
game JOIN eteam ON (team1=eteam.id) or game JOIN eteam ON (team2=eteam.id)

Notice that because id is a column name in both game and eteam you must specify eteam.id instead of just id

List the the dates of the matches and the name of the team in which 'Fernando Santos' was the team1 coach.

SELECT mdate,teamname
  FROM game JOIN eteam ON (team1=eteam.id)
WHERE coach='Fernando Santos'

List the player for every goal scored in a game where the stadium was 'National Stadium, Warsaw'

SELECT player
  FROM goal JOIN game ON (id=matchid)
 WHERE stadium = 'National Stadium, Warsaw'

More difficult questions

The example query shows all goals scored in the Germany-Greece quarterfinal.

Instead show the name of all players who scored a goal against Germany.

Select goals scored only by non-German players in matches where GER was the id of either team1 or team2.

You can use teamid!='GER' to prevent listing German players.

You can use DISTINCT to stop players being listed twice.

SELECT player, gtime
  FROM game JOIN goal ON matchid = id 
    WHERE (team1='GER' AND team2='GRE')

SELECT DISTINCT player
  FROM game JOIN goal ON matchid = id 
 WHERE (team1 = 'GER' OR team2 = 'GER')
   AND teamid!='GER'

Show teamname and the total number of goals scored.

You should COUNT(*) in the SELECT line and GROUP BY teamname

SELECT teamname, player
  FROM eteam JOIN goal ON id=teamid
 ORDER BY teamname

SELECT teamname,COUNT(teamid)
  FROM eteam JOIN goal ON id=teamid
GROUP BY teamname

Show the stadium and the number of goals scored in each stadium.

SELECT stadium,COUNT(1)
  FROM goal JOIN game ON id=matchid
GROUP BY stadium

For every match involving 'POL', show the matchid, date and the number of goals scored.

SELECT matchid,mdate, team1, team2,teamid
  FROM game JOIN goal ON matchid = id 
 WHERE (team1 = 'POL' OR team2 = 'POL')

SELECT matchid,mdate,COUNT(teamid)
  FROM game JOIN goal ON matchid = id 
 WHERE (team1 = 'POL' OR team2 = 'POL')
GROUP BY matchid,mdate

For every match where 'GER' scored, show matchid, match date and the number of goals scored by 'GER'

SELECT matchid,mdate,COUNT(teamid)
  FROM game JOIN goal ON matchid = id 
 WHERE (teamid='GER')
GROUP BY matchid,mdate

List every match with the goals scored by each team as shown. This will use "CASE WHEN" which has not been explained in any previous exercises.

mdate	team1	score1	team2	score2
1 July 2012	ESP	4	ITA	0
10 June 2012	ESP	1	ITA	1
10 June 2012	IRL	1	CRO	3
...

Notice in the query given every goal is listed. If it was a team1 goal then a 1 appears in score1, otherwise there is a 0. You could SUM this column to get a count of the goals scored by team1. Sort your result by mdate, matchid, team1 and team2.

SELECT mdate,
  team1,
  CASE WHEN teamid=team1 THEN 1 ELSE 0 END score1
  FROM game JOIN goal ON matchid = id

SELECT mdate,
  team1,
  SUM(CASE WHEN teamid=team1 THEN 1 ELSE 0 END) score1,
  team2,
  SUM(CASE WHEN teamid=team2 THEN 1 ELSE 0 END) score2
  FROM game LEFT JOIN goal ON matchid = id 
GROUP BY mdate,matchid,team1,team2

Clear your results

JOIN Quiz

Old JOIN Tutorial

The next tutorial about the Movie database involves some slightly more complicated joins.