Difference between revisions of "The JOIN operation"
Line 87: | Line 87: | ||
<div class='qu'> | <div class='qu'> | ||
− | + | This example is using JOIN to display all goals scored during the UEFA EURO 2012 final (it was the only match in July). | |
− | <p class='imper'>Show | + | <p class='imper'>Show all goals scored in Germany - Greece match. Use team1 and team2 values to find the match. |
− | |||
<source lang='sql' class='def'> | <source lang='sql' class='def'> | ||
− | SELECT | + | SELECT player, gtime FROM goal |
− | WHERE | + | JOIN game ON id = matchid |
+ | WHERE mdate LIKE '%July%' | ||
</source> | </source> | ||
<source lang='sql' class='ans'> | <source lang='sql' class='ans'> | ||
− | SELECT | + | SELECT player, gtime FROM goal |
− | + | JOIN game ON id = matchid | |
− | + | WHERE team1 = 'GER' AND team2 = 'GRE' | |
</source> | </source> | ||
</div> | </div> |
Revision as of 14:19, 2 August 2012
JOIN and UEFA EURO 2012
This tutorial introduces JOIN which allows you to use data from two or more tables. The tables contain all matches and goals from UEFA EURO 2012 Football Championship in Poland and Ukraine.
The first example shows the goal scored by 'Wayne Rooney'.
Show matchid and player name for all goals scored by English players.
teamid = 'ENG'
SELECT * FROM goal
WHERE player LIKE '%Rooney'
SELECT matchid, player
FROM game JOIN goal ON matchid = id
WHERE teamid LIKE 'ENG'
This example shows all the games played in Warsaw.
Show date, team1 and team2 for all matches that Polish ('POL') and Czech ('CZE') teams played in Warsaw.
SELECT mdate, team1, team2 FROM game
WHERE stadium = 'National Stadium, Warsaw'
SELECT mdate, team1, team2 FROM game
WHERE stadium = 'National Stadium, Warsaw'
AND (team1 = 'POL' OR team1 = 'CZE')
This query shows names of coaches from Germany and England.
Show team name of the teams which have coaches who's names start with 'M'.
SELECT coach from eteam
WHERE teamname = 'Germany'
OR teamname = 'England'
SELECT teamname from eteam
WHERE coach LIKE 'M%'
The following query shows coaches of teams that played on 9 June 2012. JOIN
has been used to make relation between game
and eteam
tables.
Show stadium and mdate of matches played by Vicente del Bosque's team.
teamid = 'ENG'
SELECT coach, mdate FROM eteam JOIN game
ON (team1 = eteam.id OR team2 = eteam.id)
WHERE mdate = '9 June 2012'
SELECT stadium, mdate FROM eteam JOIN game
ON (team1 = eteam.id OR team2 = eteam.id)
WHERE coach= 'Vicente del Bosque'
This example is using JOIN to display all goals scored during the UEFA EURO 2012 final (it was the only match in July).
Show all goals scored in Germany - Greece match. Use team1 and team2 values to find the match.
SELECT player, gtime FROM goal
JOIN game ON id = matchid
WHERE mdate LIKE '%July%'
SELECT player, gtime FROM goal
JOIN game ON id = matchid
WHERE team1 = 'GER' AND team2 = 'GRE'
</div>
More difficult questions
<p class='imper'>Show names of all non-German players who scored a goal in matches against Germany.</p>
SELECT player, gtime
FROM game JOIN goal ON matchid = id
WHERE (team1 = "GER" AND team2 = "GRE")
SELECT player
FROM game JOIN goal ON matchid = id
WHERE (team1 = "GER" OR team2 = "GER")
AND teamid != "GER"
The example shows result of the final match. COUNT()
has been used to count the total number of goals.
select team1, team2,
(select count(*) from goal
where matchid = id AND teamid = team1)
as team1,
(select count(*) from goal
where matchid = id AND teamid = team2)
as team2
FROM game WHERE id = 1031
select team1, team2,
(select count(*) from goal
where matchid = id AND teamid = team1)
as team1,
(select count(*) from goal
where matchid = id AND teamid = team2)
as team2
FROM game WHERE stadium = 'PGE Arena Gdansk'
The following query shows matches which were won by team1.
select team1, team2 FROM game WHERE
(select count(*) from goal
where matchid = id AND teamid = team1) >
(select count(*) from goal
where matchid = id AND teamid = team2)
select id FROM game WHERE
(select count(*) from goal
where matchid = id AND teamid = team1) -
(select count(*) from goal
where matchid = id AND teamid = team2) >= 2
The example shows teams that scored a goal at stadiums where Poland has played its matches.
DISTINCT
to remove duplicates from your query results.SELECT distinct teamid
FROM game JOIN goal ON matchid = id
WHERE Stadium IN
(SELECT stadium FROM game
WHERE team1 = 'POL' OR team2 = 'POL')
SELECT DISTINCT player
FROM game JOIN goal ON matchid = id
WHERE stadium = 'National Stadium, Warsaw'
AND mdate NOT IN
(SELECT mdate FROM game
WHERE team1 = 'CZE' OR team2 = 'CZE')
The query shows the stadiums, where the teams who scored more than 8 goals played their matches.
SELECT teamid, count(*) FROM goal
WHERE 3 <
(SELECT COUNT(distinct id) FROM game
WHERE team1 = teamid OR team2 = teamid)
group by teamid
SELECT distinct stadium
FROM game WHERE team1 IN
(SELECT teamid FROM goal
group by teamid having count(*) > 8)