Question

我正在尝试获取我的数据库中每个团队的赢/输记录。我觉得我很接近，但我似乎无法迈出最后一步。

表格如下所示：

GameID | TeamAID | TeamBID | Winner
-----------------------------------
  1         1         2        1
  2         3         5        3
 ...       ...       ...      ...

使用我的尝试链接到MySQL Fiddle：http://sqlfiddle.com/#!2/26b00/7

我解决这个问题的方法是首先找到每支球队的比赛次数，然后找出每支球队的胜利次数，最后从比赛中减去胜利数来获得赔率。

我想出的查询游戏数量的查询如下：

SELECT Game.TeamAID, TA.Count + TB.Count AS Sum
FROM Game
LEFT JOIN (SELECT TeamAID, COUNT(GameID) AS Count
           FROM Game
           GROUP BY TeamAID) AS TA ON TA.TeamAID = Game.TeamAID
LEFT JOIN (SELECT TeamBID, COUNT(GameID) AS Count
           FROM Game
           GROUP BY TeamBID) AS TB ON TB.TeamBID = Game.TeamAID
GROUP BY TeamAID

这成功地为我提供了每个参加过比赛的球队以及球队比赛的数量。

接下来是问题出现的时候。

这是我给出的每个团队获胜次数的查询：

SELECT Game.TeamAID, TA.Cnt + TB.Cnt AS Sum
FROM Game
LEFT JOIN (SELECT TeamAID, COUNT(GameID) AS Cnt
           FROM Game
           WHERE TeamAID = Winner
           GROUP BY TeamAID
           ORDER BY TeamAID) AS TA ON TA.TeamAID = Game.TeamAID
LEFT JOIN (SELECT TeamBID, COUNT(GameID) AS Cnt
           FROM Game
           WHERE TeamBID = Winner
           GROUP BY TeamBID
           ORDER BY TeamBID) AS TB ON TB.TeamBID = Game.TeamAID
GROUP BY TeamAID;

这给我的问题是，在某些情况下，当某个特定团队在作为TeamA或TeamB玩游戏时没有赢得任何比赛时，它会在联接后返回null。

有没有办法获得每个团队赢得的游戏数量，这样我就不会得到结果为null的问题？或者更好的是，我忽略了一个更简单的问题解决方案吗？

我最终希望结果看起来像：

TeamID | Wins | Losses
----------------------
  6       18      1
 ...      ...    ...

感谢Adam V带领我找到了帮助我解决问题的IFNULL功能。

解决方案如下：

SELECT Game.TeamAID, GP.Sum AS GamesWon, ((TA.CA + TB.CB) - GP.Sum) AS GameLost
FROM Game

LEFT JOIN (SELECT TeamAID, COUNT(GameID) AS CA
           FROM Game
           GROUP BY TeamAID
          ) AS TA ON TA.TeamAID = Game.TeamAID

LEFT JOIN (SELECT TeamBID, COUNT(GameID) AS CB
           FROM Game
           GROUP BY TeamBID
          ) AS TB ON TB.TeamBID = Game.TeamAID

LEFT JOIN (SELECT Game.TeamAID, IFNULL(TA.Cnt,0)  + IFNULL(TB.Cnt,0) AS Sum
           FROM Game
           LEFT JOIN (SELECT TeamAID, COUNT(GameID) AS Cnt
                      FROM Game
                      WHERE TeamAID = Winner
                      GROUP BY TeamAID
                      ORDER BY TeamAID
                     ) AS TA ON TA.TeamAID = Game.TeamAID
           LEFT JOIN (SELECT TeamBID, COUNT(GameID) AS Cnt
                      FROM Game
                      WHERE TeamBID = Winner
                      GROUP BY TeamBID
                      ORDER BY TeamBID
                     ) AS TB ON TB.TeamBID = Game.TeamAID
           GROUP BY TeamAID
          ) AS GP ON GP.TeamAID = Game.TeamAID

GROUP BY TeamAID

查找MySQL数据库中所有团队的赢/输记录

0 个答案: