JOIN Tutorial

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game Table

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 Table

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 Table

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

1. The first example shows the goal scored by a player with the last name 'Bender'. The * says to list all the columns in the table - a shorter way of saying matchid, teamid, player, gtime Modify it to show the matchid and player name for all goals scored by Germany. To identify German players, check for: teamid = 'GER'

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

1. From the previous query you can see that Lars Bender's scored a goal in game 1012. Now we want to know what teams were playing in that match. Notice that the column matchid in the goaltable corresponds to the id column in the game table. We can look up information about game 1012 by finding that row in the game table. Show id, stadium, team1, team2 for just game 1012

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

1. Modify it to show the player, teamid, stadium and mdate for every German goal.

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

1. 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 gm.team1, gm.team2, go.player
FROM game gm
JOIN goal go ON (gm.id=go.matchid)
WHERE player LIKE 'Mario%'

5. The table eteam gives details of every national team including the coach. You can JOIN goal to eteamusing 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 go.player, go.teamid, et.coach, go.gtime
FROM goal go
JOIN eteam et ON (go.teamid = et.id)
WHERE go.gtime <= 10

1. 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 gameand eteam you must specify eteam.id instead of just id List the dates of the matches and the name of the team in which 'Fernando Santos' was the team1 coach.

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

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

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

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

-- or
-- WHERE go.teamid != 'GER' AND (gm.team1 = 'GER' OR gm.team2='GER')

1. Show teamname and the total number of goals scored.

SELECT et.teamname, COUNT(go.player) as goals_scored
FROM eteam et
JOIN goal go
ON et.id = go.teamid
GROUP BY et.teamname

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

SELECT gm.stadium, COUNT(go.player) as goals_scored
FROM game gm
JOIN goal go ON (gm.id=go.matchid)
GROUP BY gm.stadium

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

SELECT go.matchid, gm.mdate, COUNT(go.player) as goals_scored
FROM game gm
JOIN goal go 
ON gm.id = go.matchid AND (gm.team1 = 'POL' OR gm.team2 = 'POL')
GROUP BY go.matchid, gm.mdate

-- or
-- ON gm.id = go.matchid 
-- WHERE gm.team1 = 'POL' or gm.team2 = 'POL'

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

SELECT go.matchid, gm.mdate, COUNT(go.player) as goals_scored
FROM game gm
JOIN goal go 
ON gm.id = go.matchid AND go.teamid = 'GER'
GROUP BY go.matchid, gm.mdate

-- or
-- ON goal.matchid = game.id
-- WHERE teamid = 'GER'

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