到目前为止，我有这个。
SELECT p1.player_id, p1.real_name, p2.player_id, p2.real_name,
-> m.scoreA, m.scoreB
-> FROM matches m
-> JOIN players p1 ON p1.player_id = m.playerA
-> JOIN players p2 ON p2.player_id = m.playerB;
+-----------+------------------------------------+-----------+------------------------------------+--------+--------+
| player_id | real_name | player_id | real_name | scoreA | scoreB |
+-----------+------------------------------------+-----------+------------------------------------+--------+--------+
| 19 | Seong Hun Choi | 1 | Dong Nyoung Lee | 0 | 2 |
| 38 | Yun Sik Choi | 1 | Dong Nyoung Lee | 0 | 2 |
| 160 | Lei Wang | 1 | Dong Nyoung Lee | 0 | 2 |
| 3 | Seung Hyun Lee | 1 | Dong Nyoung Lee | 0 | 2 |
| 45 | Min Chul Kim | 1 | Dong Nyoung Lee | 0 | 2 |
| 23 | Sasha Hostyn | 1 | Dong Nyoung Lee | 2 | 4 |
| 52 | Juan Moreno Duran | 1 | Dong Nyoung Lee | 2 | 3 |
| 18 | Kang Dong Hyun | 1 | Dong Nyoung Lee | 2 | 1 |
| 22 | Jae Duck Lim | 1 | Dong Nyoung Lee | 1 | 2 |
| 108 | Jérémy Vansnick | 1 | Dong Nyoung Lee | 1 | 2 |
我想加入我的members 表中的更多列，而不改变我的匹配表 的大小。我尝试的一切似乎都会改变我的匹配表的大小。它从 46k 增加到超过 100 万。到目前为止，这是我尝试过的。
SELECT p1.player_id, p1.real_name, p2.player_id, p2.real_name,
m.scoreA, m.scoreB, mem1.player, mem2.player
FROM matches m
JOIN players p1 ON p1.player_id = m.playerA
JOIN members mem1 ON mem1.player = p1.player_id
JOIN players p2 ON p2.player_id = m.playerB
JOIN members mem2 ON mem2.player = p2.player_id;
我想也许我设置的相等部分有误，所以我尝试了这个。
SELECT p1.player_id, p1.real_name, p2.player_id, p2.real_name,
m.scoreA, m.scoreB, mem1.player, mem2.player
FROM matches m
JOIN players p1 ON p1.player_id = m.playerA
JOIN members mem1 ON mem1.player = m.playerA
JOIN players p2 ON p2.player_id = m.playerB
JOIN members mem2 ON mem2.player = m.playerB;
我希望它完成后看起来像这样。
+-----------+------------------------------------+-----------+------------------------------------+--------+--------+
| player_id | real_name | player_id | real_name | scoreA | scoreB | member1 member2
+-----------+------------------------------------+-----------+------------------------------------+--------+--------+
| 19 | Seong Hun Choi | 1 | Dong Nyoung Lee | 0 | 2 |
| 38 | Yun Sik Choi | 1 | Dong Nyoung Lee | 0 | 2 |
| 160 | Lei Wang | 1 | Dong Nyoung Lee | 0 | 2 |
| 3 | Seung Hyun Lee | 1 | Dong Nyoung Lee | 0 | 2 |
| 45 | Min Chul Kim | 1 | Dong Nyoung Lee | 0 | 2 |
| 23 | Sasha Hostyn | 1 | Dong Nyoung Lee | 2 | 4 |
| 52 | Juan Moreno Duran | 1 | Dong Nyoung Lee | 2 | 3 |
| 18 | Kang Dong Hyun | 1 | Dong Nyoung Lee | 2 | 1 |
| 22 | Jae Duck Lim | 1 | Dong Nyoung Lee | 1 | 2 |
| 108 | Jérémy Vansnick | 1 | Dong Nyoung Lee | 1 | 2 |
| 53 | Igor Turchin | 1 | Dong Nyoung Lee | 1 | 2 |
| 17 | Hyun Woo Park | 1 | Dong Nyoung Lee | 0 | 2 |
我还需要用另外两个表重复此过程，因此非常感谢帮助我理解如何执行此操作的过程。
匹配表。
+----------+------------+------------+---------+---------+--------+--------+---------+
| match_id | date | tournament | playerA | playerB | scoreA | scoreB | offline |
+----------+------------+------------+---------+---------+--------+--------+---------+
| 1 | 2012-12-04 | 799 | 4 | 55 | 1 | 3 | 0 |
| 2 | 2012-12-03 | 11921 | 2 | 41 | 2 | 0 | 0 |
| 3 | 2012-12-03 | 11921 | 21 | 41 | 0 | 2 | 0 |
| 4 | 2012-12-03 | 11921 | 3 | 2 | 2 | 1 | 0 |
| 5 | 2012-12-03 | 11921 | 41 | 2 | 1 | 2 | 0 |
| 6 | 2012-12-03 | 11921 | 21 | 3 | 1 | 2 | 0 |
| 7 | 2012-12-03 | 11924 | 1 | 8 | 2 | 1 | 1 |
| 8 | 2012-12-03 | 11924 | 1 | 8 | 2 | 3 | 1 |
| 9 | 2012-12-03 | 11924 | 8 | 19 | 3 | 2 | 1 |
| 10 | 2012-12-03 | 11924 | 19 | 12 | 2 | 1 | 1 |
+----------+------------+------------+---------+---------+--------+--------+---------+
玩家表
+-----------+-----------+-----------------+-------------+------------+-----------+
| player_id | tag | real_name | nationality | birthday | game_race |
+-----------+-----------+-----------------+-------------+------------+-----------+
| 1 | Leenock | Dong Nyoung Lee | KR | 1995-04-01 | Z |
| 2 | Creator | Hyun Woo Jang | KR | 1996-08-19 | P |
| 3 | Life | Seung Hyun Lee | KR | 1997-01-11 | Z |
| 4 | DongRaeGu | Soo Ho Park | KR | 1991-06-03 | Z |
| 5 | PartinG | Lee Sak Won | KR | 1994-08-24 | P |
| 6 | TaeJa | Young Suh Yoon | KR | 1995-01-01 | T |
| 7 | Rain | Yoon Jong Jung | KR | 1992-08-14 | P |
| 8 | viOLet | Dong Hwan Kim | KR | 1990-12-05 | Z |
| 9 | Sniper | Tae Hoon Kwon | KR | 1995-01-22 | Z |
| 10 | Stephano | Ilyes Satouri | FR | 1993-03-12 | Z |
+-----------+-----------+-----------------+-------------+------------+-----------+
成员表
+--------+------+------------+------------+
| player | team | start_date | end_date |
+--------+------+------------+------------+
| 1 | 88 | 2011-02-23 | 2011-07-18 |
| 1 | 4 | 2011-07-18 | NULL |
| 2 | 3 | 2011-01-12 | NULL |
| 3 | 65 | 2010-10-19 | 2012-07-13 |
| 3 | 1 | 2012-07-13 | NULL |
| 4 | 7 | 2011-02-20 | NULL |
| 5 | 88 | 2010-10-29 | 2011-07-18 |
| 5 | 1 | 2012-10-21 | 2013-01-03 |
| 5 | 12 | 2013-01-14 | NULL |
| 6 | 65 | 2011-03-01 | 2011-05-01 |
+--------+------+------------+------------+
最佳答案
看起来查询正在生成半笛卡尔积。
player 列在 member 表中不是唯一的。根据 start_date 和 end_date，看起来 player 一次只能是一个团队的 member .
我们可能希望将 match 表中的 date 与 start_date 和 end_date 进行比较在 member 表中。我们可能还希望将其设为外部联接。
LEFT
JOIN `member` mem2
ON mem2.player = m.playerB
AND mem2.start_date <= m.date
AND ( mem2.end_date > m.date OR mem2.end_date IS NULL )
请注意，其中一个日期比较包括相等性，另一侧不包括(因为行上的 start_date 似乎等于另一行上的 end_date在 member 中，对于相同的 player。
(对于一场比赛 date='2011-07-18'，player=1 是哪支球队的成员？)
我们还想处理 end_date 中的 NULL 值，在这种情况下，它代表一个大于 match 的大值> 日期。
我们也想对 mem1 使用相同的模式。
关于mysql - 同一张表上的多个连接，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47523590/