Question

我正在尝试运行SQL查询以显示竞赛中一组战斗的结果。战斗细节存储在战斗机1，战斗机2和胜利者的领域。我需要做的就是把所有战斗的列表放在一起，每个战斗在列表中出现两次 - 例如，一次用

Competitor:fighter1, Opponent:fighter2, Winner:fighter1

以及列表中的其他地方

Competitor:fighter2, Opponent:fighter1, Winner:fighter1

我一直在使用sql union来从每次战斗中提取两次细节，并尝试为fighter1和fighter2列分配不同的别名来交换它们，但我甚至不确定这是否可能。< / p>

我的查询是这样的（省略了其他表中的不必要的东西）

SELECT wp_ema_fights.fighter1 AS competitor,
wp_ema_fights.fighter2 AS opponent, 
wp_ema_fights.winner AS winner
FROM wp_ema_fights
UNION ALL
SELECT wp_ema_fights.fighter1 AS opponent,
wp_ema_fights.fighter2 AS competitor,   
wp_ema_fights.winner AS winner
FROM wp_ema_fights
ORDER BY competitor

此查询显示每次战斗两次，但是像这样：

Competitor:fighter1, Opponent:fighter2, Winner:fighter1
Competitor:fighter1, Opponent:fighter2, Winner:fighter1

有没有人知道如何交换这两个并且每次都被指定为“竞争对手”的战斗机订购列表？

提前致谢。

Answer 1

尝试：

SELECT   wp_ema_fights.fighter1 AS competitor,
         wp_ema_fights.fighter2 AS opponent,
         wp_ema_fights.winner AS winner
FROM     wp_ema_fights
UNION ALL
SELECT   wp_ema_fights.fighter2 AS competitor,
         wp_ema_fights.fighter1 AS opponent,
         wp_ema_fights.winner AS winner
FROM     wp_ema_fights
ORDER BY competitor

Answer 2

除了Xophmester的回答，你可以用连接而不是UNION来做。这具有仅加载源数据一次而不是两次的优点。（这与非常大的数据集更相关，而不仅仅是小数据集。）

SELECT   CASE WHEN Mode.ID = 1 THEN wp_ema_fights.fighter1 ELSE wp_ema_fights.fighter2 END AS competitor,
         CASE WHEN Mode.ID = 2 THEN wp_ema_fights.fighter2 ELSE wp_ema_fights.fighter1 END AS opponent,
         wp_ema_fights.winner AS winner
FROM     wp_ema_fights
CROSS JOIN (SELECT 1 as ID UNION ALL SELECT 2 as ID) AS Mode
ORDER BY CASE WHEN Mode.ID = 1 THEN wp_ema_fights.fighter1 ELSE wp_ema_fights.fighter2 END

Answer 3

我认为UNION会忽略不匹配的列名称，并根据列在两个SELECT语句中的显示顺序对列进行排序。

因此，只需在第二个.fighter1中交换.fighter2和SELECT。

Answer 4

尝试：

SELECT wp_ema_fights.fighter1 AS competitor,
wp_ema_fights.fighter2 AS opponent, 
wp_ema_fights.winner AS winner
FROM wp_ema_fights
UNION ALL
SELECT wp_ema_fights.fighter2 AS competitor,
wp_ema_fights.fighter1 AS opponent,   
wp_ema_fights.winner AS winner
FROM wp_ema_fights
ORDER BY competitor

Answer 5

如果您的SQL产品支持它，请将UNION ALL更改为UNION CORRESPONDING。

如果两个'OR'条件都为真，则返回相同的行

5 个答案: