无法显示每个玩家赢得的比赛、进行的比赛和平局的比赛

Question

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
);

我似乎无法正确计算赢得比赛的次数。我认为问题与匹配表的左连接有关。

这个想法是从匹配表中的result 列中读取结果被解释为：

0 = draw
1 = player1 won
2 = player2 won 

使用当前模式，我可以正确获取每个玩家的比赛次数，但不能正确获得比赛次数。

如果可能的话，我还希望在不必分解为多个视图或表格的情况下添加并列比赛的数量。有什么建议吗？

Answer 1

由于您没有包含所有架构，因此我做了一些有根据的猜测，并提出了我认为应该可行的观点。我添加了一些额外的输赢和平局计数，并且我发现更容易在视图中显示所有结果来验证结果。

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
);

这是我创建的 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
);

查询 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 |