sql - 无法显示获胜的比赛，比赛的进行以及每个球员的比赛

CREATE TABLE matches (
  match_id BIGSERIAL PRIMARY KEY,
  tournamentid INTEGER,
  player1_id INTEGER,
  player2_id INTEGER CHECK (player1_id < player2_id),
  result INTEGER CHECK (result IN (0, 1, 2)),
  FOREIGN KEY(tournamentid, player1_id) REFERENCES enroll(tournament, player_id),
  FOREIGN KEY(tournamentid, player2_id) REFERENCES enroll(tournament, player_id),
  UNIQUE(tournamentid, player1_id, player2_id)
);

CREATE VIEW player_standings AS (
SELECT tournaments.tournament_id,
     tournaments.tournament_name,
     enroll.player_id,
     players.name,
     CASE
          WHEN matches.result = 1 THEN COUNT(matches.player1_id)
          WHEN matches.result = 2 THEN COUNT(matches.player2_id)
          END AS wins,

     COUNT(enroll.player_id IN (matches.player1_id, matches.player2_id)) AS match_played

FROM players
  INNER JOIN enroll ON enroll.player_id = players.id
  INNER JOIN tournaments ON tournaments.tournament_id = enroll.tournament
  LEFT JOIN matches ON (matches.player1_id = enroll.player_id) or
       (matches.player2_id = enroll.player_id)

GROUP BY tournaments.tournament_id, tournaments.tournament_name,
    enroll.player_id, players.name, matches.result
ORDER BY tournaments.tournament_id, wins DESC
);

我似乎不能正确地计算出获胜的比赛次数。我认为这个问题与matches表的左连接有关。
其思想是从matches表的result列中读取结果，其中的结果解释为：

0 = draw
1 = player1 won
2 = player2 won

使用当前的模式，我可以正确地获得每个玩家的比赛次数，但不能得到比赛次数。
如果可能的话，我还希望添加绑定的匹配数，而不必拆分成多个视图或表。有什么建议吗？

最佳答案

因为你没有包括你所有的模式，我做了一些有根据的猜测，并提出了这个观点，我认为应该工作。我包括了一些额外的损失计数和抽签，我发现更容易验证结果与所有的结果在视图中出现。

CREATE VIEW player_standings AS (
SELECT
      tournaments.tournament_id as t_id
    , tournaments.tournament_name
    , enroll.player_id
    , players.name
    , COUNT(
       CASE
        WHEN enroll.player_id = matches.player1_id AND matches.result = 1 THEN 1
        WHEN enroll.player_id = matches.player2_id AND matches.result = 2 THEN 1
       END) AS wins
    , COUNT(
       CASE
        WHEN enroll.player_id = matches.player1_id AND matches.result = 2 THEN 1
        WHEN enroll.player_id = matches.player2_id AND matches.result = 1 THEN 1
       END) AS losses
    , COUNT(CASE WHEN matches.result = 0 THEN 1 END) AS draws
    , COUNT(match_id) AS matches_played

FROM players
INNER JOIN enroll ON enroll.player_id = players.id
INNER JOIN tournaments ON tournaments.tournament_id = enroll.tournament
LEFT JOIN matches ON matches.tournamentid = tournaments.tournament_id
                 AND enroll.player_id IN (matches.player1_id, matches.player2_id)
GROUP BY
  tournaments.tournament_id,
  tournaments.tournament_name,
  enroll.player_id,
  players.name
ORDER BY
  tournaments.tournament_id,
  wins DESC,
  matches_played DESC
);

下面是我创建的SQL Fiddle的降价输出：
SQL Fiddle
PostgreSQL 9.3架构设置：

create table players (
  id int primary key,
  name varchar(20)
);

insert into players values
(1, 'Player 1'),(2, 'Player 2'),
(3, 'Player 3'),(4, 'Player 4'),(5, 'Player 5');

create table tournaments (
  tournament_id int primary key,
  tournament_name varchar(20)
);

insert into tournaments values (1, 'Tournament 1'),(2, 'Tournament 2');

create table enroll (
  tournament int,
  player_id int,
  primary key (tournament, player_id),
  foreign key (tournament) references tournaments(tournament_id),
  foreign key (player_id) references players(id)
);

insert into enroll values
(1,1),(1,2),(1,3),(1,4),(1,5),
(2,1),(2,2),(2,3),(2,4),(2,5);

CREATE TABLE matches (
  match_id bigserial PRIMARY KEY,
  tournamentid INTEGER,
  player1_id INTEGER,
  player2_id INTEGER CHECK (player1_id < player2_id),
  result INTEGER CHECK (result IN (0, 1, 2)),
  FOREIGN KEY(tournamentid, player1_id) REFERENCES enroll(tournament, player_id),
  FOREIGN KEY(tournamentid, player2_id) REFERENCES enroll(tournament, player_id),
  UNIQUE(tournamentid, player1_id, player2_id)
);

insert into matches (tournamentid, player1_id, player2_id, result) values
 (1, 1, 2, 1) -- 1 win 2 loss
,(1, 1, 3, 1) -- 1 win 3 loss
,(1, 2, 3, 2) -- 2 win 2 loss
,(1, 1, 5, 1) -- 1 win 5 loss

,(2, 2, 4, 0) -- 2 draw 4 draw
,(2, 1, 2, 1) -- 1 win 2 loss
,(2, 3, 4, 2) -- 4 win 3 loss
;

CREATE VIEW player_standings AS (
SELECT
      tournaments.tournament_id as t_id
    , tournaments.tournament_name
    , enroll.player_id
    , players.name
    , COUNT(
       CASE
        WHEN enroll.player_id = matches.player1_id AND matches.result = 1 THEN 1
        WHEN enroll.player_id = matches.player2_id AND matches.result = 2 THEN 1
       END) AS wins
    , COUNT(
       CASE
        WHEN enroll.player_id = matches.player1_id AND matches.result = 2 THEN 1
        WHEN enroll.player_id = matches.player2_id AND matches.result = 1 THEN 1
       END) AS losses
    , COUNT(CASE WHEN matches.result = 0 THEN 1 END) AS draws
    , COUNT(match_id) AS matches_played

FROM players
INNER JOIN enroll ON enroll.player_id = players.id
INNER JOIN tournaments ON tournaments.tournament_id = enroll.tournament
LEFT JOIN matches ON matches.tournamentid = tournaments.tournament_id
                 AND enroll.player_id IN (matches.player1_id, matches.player2_id)
GROUP BY
  tournaments.tournament_id,
  tournaments.tournament_name,
  enroll.player_id,
  players.name
ORDER BY
  tournaments.tournament_id,
  wins DESC,
  matches_played DESC
);

问题1：

select * from player_standings

Results：

| t_id | tournament_name | player_id |     name | wins | losses | draws | matches_played |
|------|-----------------|-----------|----------|------|--------|-------|----------------|
|    1 |    Tournament 1 |         1 | Player 1 |    3 |      0 |     0 |              3 |
|    1 |    Tournament 1 |         3 | Player 3 |    1 |      1 |     0 |              2 |
|    1 |    Tournament 1 |         2 | Player 2 |    0 |      2 |     0 |              2 |
|    1 |    Tournament 1 |         5 | Player 5 |    0 |      1 |     0 |              1 |
|    1 |    Tournament 1 |         4 | Player 4 |    0 |      0 |     0 |              0 |
|    2 |    Tournament 2 |         4 | Player 4 |    1 |      0 |     1 |              2 |
|    2 |    Tournament 2 |         1 | Player 1 |    1 |      0 |     0 |              1 |
|    2 |    Tournament 2 |         2 | Player 2 |    0 |      1 |     1 |              2 |
|    2 |    Tournament 2 |         3 | Player 3 |    0 |      1 |     0 |              1 |
|    2 |    Tournament 2 |         5 | Player 5 |    0 |      0 |     0 |              0 |

关于sql - 无法显示获胜的比赛，比赛的进行以及每个球员的比赛，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/31484776/