從SQL中的多個列計數值

Question

對於體育比賽，當人們與2名球員組成的另一支球隊成對比賽時，我想輸出一個特定球員面對的每個對手的列表，以及特定球員之間的勝負數目。玩家和那個對手。

例如，如果結果為：

1. 玩家1和玩家2 2-1玩家3和玩家4
2. 玩家3和玩家1 1-0玩家2和玩家4
3. 玩家2和玩家4 4-2玩家1和玩家3
4. 玩家1和玩家4 0-0玩家3和玩家2

我希望播放器1的輸出為：

• 玩家2，W1 D1 L1
• 播放器3，W1 D1 L0
• 播放器4，W2 D0 L1

事實證明，這很難實現。 我的數據分為兩個表，一個是所有玩家的表（Players），一個是分數表（Scores）。

玩家具有字段PlayerID和PlayerName。

得分具有字段Player1，Player2，Player3，Player4和Score，其中每個Player字段都可以包含任何PlayerID（因此，任何給定的ID可能會根據行而出現在不同的列中），並且存儲得分，如果得分小於21，玩家1和2輸了，如果大於21，他們贏了。

此查詢有什么問題？ 顯然它返回0。

SELECT opponent as opp, COUNT(result='win') as c1, COUNT(result='draw') as c2, COUNT(result='loss') as c3
      FROM (SELECT
            CASE
                WHEN '$player' IN(Players1.PlayerName, Players2.PlayerName) THEN Players3.PlayerName
                WHEN '$player' IN(Players3.PlayerName, Players4.PlayerName) THEN Players1.PlayerName
                ELSE 'NA' 
                END as opponent,
            CASE
                WHEN '$player' IN(Players1.PlayerName, Players2.PlayerName) 
                THEN
                    CASE
                        WHEN Scores.Score > 21 THEN 'win'
                        ELSE 'NA'
                        END as result,
                    CASE
                        WHEN Scores.Score < 21 THEN 'loss'
                        ELSE 'NA'
                        END as result,
                WHEN '$player' IN(Players3.PlayerName, Players4.PlayerName) 
                THEN
                    CASE
                        WHEN Scores.Score < 21 THEN 'win'
                        ELSE 'NA'
                        END as result,
                    CASE
                        WHEN Scores.Score > 21 THEN 'loss'
                        ELSE 'NA'
                        END as result,
                WHEN Scores.Score = 21 THEN 'draw'
                ELSE 'NA' 
                END as result,
        FROM Scores
        INNER JOIN Players Players1 ON Scores.Player1=Players1.PlayerID
        INNER JOIN Players Players2 ON Scores.Player2=Players2.PlayerID
        INNER JOIN Players Players3 ON Scores.Player3=Players3.PlayerID
        INNER JOIN Players Players4 ON Scores.Player4=Players4.PlayerID
        WHERE Players1.PlayerName = '$player' OR Players2.PlayerName = '$player' OR Players3.PlayerName = '$player' OR Players4.PlayerName = '$player'
        UNION ALL
        SELECT
            CASE
                WHEN '$player' IN(Players1.PlayerName, Players2.PlayerName) THEN Players4.PlayerName
                WHEN '$player' IN(Players3.PlayerName, Players4.PlayerName) THEN Players2.PlayerName
                ELSE 'NA' 
                END as opponent,
            CASE
                WHEN '$player' IN(Players1.PlayerName, Players2.PlayerName) AND Scores.Score > 21 THEN 'win'
                WHEN '$player' IN(Players1.PlayerName, Players2.PlayerName) AND Scores.Score < 21 THEN 'loss'
                WHEN '$player' IN(Players3.PlayerName, Players4.PlayerName) AND Scores.Score < 21 THEN 'win'
                WHEN '$player' IN(Players3.PlayerName, Players4.PlayerName) AND Scores.Score > 21 THEN 'loss'
                WHEN Scores.Score = 21 THEN 'draw'
                ELSE 'NA' 
                END as result,
        FROM Scores
        INNER JOIN Players Players1 ON Scores.Player1=Players1.PlayerID
        INNER JOIN Players Players2 ON Scores.Player2=Players2.PlayerID
        INNER JOIN Players Players3 ON Scores.Player3=Players3.PlayerID
        INNER JOIN Players Players4 ON Scores.Player4=Players4.PlayerID 
        WHERE Players1.PlayerName = '$player' OR Players2.PlayerName = '$player' OR Players3.PlayerName = '$player' OR Players4.PlayerName = '$player'
    ) AS SUBQUERY
    GROUP BY opp

Answer 1

它不是很漂亮，但是由於MySQL缺少Pivot函數，因此您可以使用內部查詢來對結果進行錘擊，從而細分誰扮演誰以及結果是什么。 然后，外部查詢可以匯總這些結果。 像下面這樣的東西對我有用，盡管再一次，它不是很漂亮 ：

select players.name as playerName, 
  opponents.name as opponentName, 
  SUM(CASE WHEN result = 'W'THEN 1 ELSE 0 END) AS win, 
  SUM(CASE WHEN result = 'L'THEN 1 ELSE 0 END) AS lose, 
  SUM(CASE WHEN result = 'D' THEN 1 ELSE 0 END) AS draw 
from  (
    select player1 as player, player3 as opponent, score, CASE WHEN score > 21 THEN 'W' WHEN score < 21 THEN 'L' ELSE 'D' END as result
    from scores
    union all
    select player1 as player, player4 as opponent, score, CASE WHEN score > 21 THEN 'W' WHEN score < 21 THEN 'L' ELSE 'D' END as result
    from scores
    union all
    select player2 as player, player3 as opponent, score, CASE WHEN score > 21 THEN 'W' WHEN score < 21 THEN 'L' ELSE 'D' END as result
    from scores
    union all
    select player2 as player, player4 as opponent, score, CASE WHEN score > 21 THEN 'W' WHEN score < 21 THEN 'L' ELSE 'D' END as result
    from scores
    -- now reverse result because opponents are being slotted into the player position
    union all
    select player3 as player, player1 as opponent, score, CASE WHEN score > 21 THEN 'L' WHEN score < 21 THEN 'W' ELSE 'D' END as result
    from scores
    union all
    select player4 as player, player1 as opponent, score, CASE WHEN score > 21 THEN 'L' WHEN score < 21 THEN 'W' ELSE 'D' END as result
    from scores
    union all
    select player3 as player, player2 as opponent, score, CASE WHEN score > 21 THEN 'L' WHEN score < 21 THEN 'W' ELSE 'D' END as result
    from scores
    union all
    select player4 as player, player2 as opponent, score, CASE WHEN score > 21 THEN 'L' WHEN score < 21 THEN 'W' ELSE 'D' END as result
    from scores
) resultsByPlayer
inner join players on players.playerId = resultsByPlayer.player
inner join players as opponents on opponents.playerId = resultsByPlayer.opponent
group by players.playerId, opponents.playerId