跨数据库字段的条件检查答案

【问题标题】：Conditional checks across database fields跨数据库字段的条件检查
【发布时间】：2012-01-09 19:49:40
【问题描述】：

我有一个包含以下字段的数据库“结果”表：

game_id, 主队，客队， home_team_score, away_team_score, 结果

目前结果字段可能有 3 个值，“H”（主队获胜）、“A”（客队获胜）或“D”（平局）。现在，要获取特定团队的所有结果，我会执行类似“SELECT * FROM results where home_team = “TEAM A”或 away_team = “TEAM A”的查询。然后在我的代码中，我必须检查是否home_team 是 TEAM A，结果是 H，那么就是胜利、平局或失败等。有没有办法可以在查询中进行此检查，以便获得类似于下面的结果列表

game_id, 主队，客队， home_team_score, away_team_score, 结果（W（赢），L（输）或D（平））

基于被查询的团队。

感谢您在网络上努力获取资源的任何帮助。

作为参考，它是一个 SQLite 数据库。

【问题讨论】：

标签： sql database sqlite

【解决方案1】：

您可以使用case 在 SQL 中计算结果：

select  *
,       case 
        when result = 'D' then 'D'
        when home_team = @YourTeam and result = 'H' then 'W'
        when away_team = @YourTeam and result = 'A' then 'W'
        else 'L'
        end as Outcome
from    YourTable
where   home_ream = @YourTeam
        or away_team = @YourTeam

【讨论】：

结果被枚举为D,A,H，而不是D,W,L ;) 另外，更重要的是，如果客队赢了，这将显示为输。

【解决方案2】：

@Andomar 的回答略有变化:)

SELECT
  *,
  CASE
    WHEN result = 'D'                             THEN 'Draw'
    WHEN home_team = @yourTeam AND result = 'H'   THEN 'Home Win'
    WHEN home_team = @yourTeam AND result = 'A'   THEN 'Home Loss'
    WHEN result = 'H'                             THEN 'Away Loss'
    ELSE                                               'Away Win'
  END
FROM
  YourTable
WHERE
     home_team = @yourTeam
  OR away_team = @yourTeam

【讨论】：

【解决方案3】：

您没有指定地点（无论是在家还是在外），但它似乎是可取的。

home/away 和 W/L//D 组合的并集易于生成且易于阅读 IMO：

CREATE VIEW YourView
(
 game_id, home_team, away_team, 
 venue, outcome
)
AS
SELECT game_id, 
       home_team AS your_team,               
       away_team AS opponent_team, 
       'H' AS venue, 'W' AS outcome
  FROM YourTable
 WHERE result = 'H'
UNION
SELECT game_id, 
       away_team AS your_team, 
       home_team AS opponent_team, 
       'A' AS venue, 'W' AS outcome
  FROM YourTable
 WHERE result = 'A'
UNION
SELECT game_id, 
       home_team AS your_team, 
       away_team AS opponent_team, 
       'H' AS venue, 'L' AS outcome
  FROM YourTable
 WHERE result = 'A'
UNION
SELECT game_id, 
       away_team AS your_team, 
       home_team AS opponent_team, 
       'A' AS venue, 'L' AS outcome
  FROM YourTable
 WHERE result = 'H'
UNION
SELECT game_id, 
       home_team AS your_team, 
       away_team AS opponent_team, 
       'H' AS venue, 'D' AS outcome
  FROM YourTable
 WHERE result = 'D'
UNION
SELECT game_id, 
       away_team AS your_team, 
       home_team AS opponent_team, 
       'A' AS venue, 'D' AS outcome
  FROM YourTable
 WHERE result = 'A';

 SELECT * 
   FROM YourView
  WHERE your_team = @your_team;

【讨论】：