我有一个包含这四个表的数据库：
CREATE TABLE team (
id CHAR(3),
name VARCHAR2(80) CONSTRAINT nn_team_name NOT NULL,
district VARCHAR2(20) CONSTRAINT nn_team_district NOT NULL,
CONSTRAINT pk_team
PRIMARY KEY (id)
);
CREATE TABLE game (
home,
away,
round NUMBER(2) CONSTRAINT nn_game_round NOT NULL,
spectators NUMBER(5),
--
CONSTRAINT pk_game
PRIMARY KEY (home, away),
--
CONSTRAINT fk_game_home
FOREIGN KEY (home)
REFERENCES team(id),
CONSTRAINT fk_game_away
FOREIGN KEY (away)
REFERENCES team(id),
--
CONSTRAINT ck_game_round
CHECK (round BETWEEN 1 AND 30),
CONSTRAINT ck_game_spectators
CHECK (spectators > 0)
);
CREATE TABLE player (
nickname NUMBER(8),
name VARCHAR2(80) CONSTRAINT nn_player_name NOT NULL,
yearOfBirth NUMBER(4) CONSTRAINT nn_player_yearOfBirth NOT NULL,
team CONSTRAINT nn_player_team NOT NULL,
--
CONSTRAINT pk_player
PRIMARY KEY (nickname),
--
CONSTRAINT fk_player_team
FOREIGN KEY (team)
REFERENCES team(id),
--
CONSTRAINT ck_player_yearOfBirth
CHECK (yearOfBirth BETWEEN 1950 AND 2000)
);
CREATE TABLE plays (
player,
home,
away,
goals NUMBER(2) CONSTRAINT nn_plays_goals NOT NULL,
--
CONSTRAINT pk_plays
PRIMARY KEY (player, home, away),
--
CONSTRAINT fk_plays_player
FOREIGN KEY (player) REFERENCES player(nickname),
CONSTRAINT fk_plays_game
FOREIGN KEY (home, away) REFERENCES game(home, away),
--
CONSTRAINT ck_plays_goals
CHECK (goals >= 0)
）;
我在这四个问题上遇到了麻烦：
答案 0 :(得分：0)
未经测试，因为我没有任何测试数据......
查询1
-- Average number of goals per game per round.
-- The result should be ordered by round number.
WITH num_games AS (
SELECT COUNT(1) AS num_games,
round
FROM game
GROUP BY round
)
SELECT g.round,
SUM( p.goals / n.num_games )
AS avg_goals_per_game_per_round
FROM game g
INNER JOIN
plays p
ON ( g.home = p.home AND g.away = p.away )
INNER JOIN
num_games n
ON ( g.round = n.round )
GROUP BY g.round
ORDER BY g.round;
查询2
-- Names and nicknames of the players, and their team id's,
-- that played away in less than five games.
-- The result should include the players that didn't played in any game.
-- There must be ONLY one SELECT clause.
SELECT p.nickname,
p.name,
p.team
FROM player p
LEFT OUTER JOIN
plays l
ON ( p.nickname = l.player )
GROUP BY p.nickname, p.name, p.team
HAVING COUNT( 1 ) < 5;
查询3
-- id's of the teams with the larger number of goals against per round.
-- In case there's more than one team with the larger number
-- of goals against, both teams should show in the result.
-- Assume the teams play in every round.
WITH player_home_or_away_goals AS (
SELECT player,
home,
away,
goals,
CASE WHEN home = (SELECT team
FROM player p
WHERE p.nickname = l.player)
THEN 'H'
ELSE 'A'
END AS home_away
FROM plays l
),
game_home_or_away_goals AS (
SELECT home,
away,
SUM( DECODE( home_away, 'H', goals, null ) ) AS home_goals,
SUM( DECODE( home_away, 'A', goals, null ) ) AS away_goals
FROM player_home_or_away_goals
GROUP BY home, away
),
team_goals_per_game_per_round AS (
SELECT g.home AS team_id,
h.home_goals AS goals_for,
h.away_goals AS goals_against,
g.round
FROM game g
INNER JOIN
game_home_or_away_goals h
ON ( g.home = h.home AND g.away = h.away )
UNION ALL
SELECT g.away AS team_id,
h.away_goals AS goals_for,
h.home_goals AS goals_against,
g.round
FROM game g
INNER JOIN
game_home_or_away_goals h
ON ( g.home = h.home AND g.away = h.away )
),
total_team_goals_per_round AS (
SELECT team_id,
round,
SUM( goals_for ) AS total_goals_for_per_round,
SUM( goals_against ) AS total_goals_against_per_round
FROM team_goals_per_game_per_round
GROUP BY team_id,
round
),
max_goals_against_per_round AS (
SELECT round,
MAX( total_goals_against_per_round ) AS greatest_goals_against
FROM total_team_goals_per_round
GROUP BY round
)
SELECT t.team_id,
t.round
FROM total_team_goals_per_round t
INNER JOIN
max_goals_against_per_round m
ON ( t.round = m.round
AND t.total_goals_against_per_round = m.greatest_goals_against );
查询4
-- Nicknames and id's of their clubs, for the players that scored
-- the larger number of goals in two, and only two games. If there
-- are more than one player in this conditions, none is shown.
请发布一些测试数据和所需的输出，因为不清楚该问题的具体要求是什么。