sqlzoo:The JOIN operation

川长思鸟来 2022-12-27 06:29 112阅读 0赞

> 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.  Show id, stadium, team1, team2 for just game 1012

SELECT id,stadium,team1,team2
    FROM game
    WHERE id = 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)
    WHERE teamid = 'GER'

> 1.  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%'

> 1.  Show player, teamid, coach, gtime for all goals scored in the first 10 minutes gtime<=10

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

> 1.  List 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 (game.team1 = eteam.id)
    WHERE coach = 'Fernando Santos'

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

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

> 1.  Instead show the name of all players who scored a goal against Germany.

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

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

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

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

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

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

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

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

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

> 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.

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 id = matchid
    GROUP BY mdate, matchid, team1, team2