Question

我有3张桌子，比赛，球员和副牌。

我想从表中选择匹配结果，并根据其ID附加玩家和套牌的相应名称。

我尝试了JOIN和WHERE，但没有结果，请参见此处的小提琴：

https://www.db-fiddle.com/f/pPmpqxaUbA6dGFT93Fa1AV/3

连接的问题是显示所有组合，而不是仅显示匹配的一个

。

    CREATE TABLE `decks` (
  `did` int(10) UNSIGNED NOT NULL,
  `name` varchar(150) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO `decks` (`did`, `name`) VALUES
(275, 'Porto'),
(276, 'Ajax'),
(277, 'Trofense'),
(278, 'Barcelona'),
(279, 'Real Madrid'),
(280, 'Braga');


CREATE TABLE `matches` (
  `mid` int(10) UNSIGNED NOT NULL,
  `tid` int(10) UNSIGNED NOT NULL,
  `did_1` int(10) UNSIGNED NOT NULL,
  `did_2` int(10) UNSIGNED NOT NULL,
  `result` int(1) NOT NULL,
  `pid_1` bigint(20) NOT NULL,
  `pid_2` bigint(20) NOT NULL,
  `valid` int(1) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;


INSERT INTO `matches` (`mid`, `tid`, `did_1`, `did_2`, `result`, `pid_1`, `pid_2`, `valid`) VALUES
(78, 2, 275, 276, 2, 35, 36, 0),
(79, 2, 277, 273, 1, 37, 38, 0),
(80, 2, 275, 278, 1, 39, 40, 0),
(81, 2, 279, 280, 1, 41, 42, 0),
(82, 2, 276, 277, 2, 36, 37, 0),
(83, 2, 275, 279, 1, 39, 41, 0),
(84, 2, 277, 275, 2, 37, 39, 0);


CREATE TABLE `players` (
  `pid` bigint(20) NOT NULL,
  `name` varchar(255) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;



INSERT INTO `players` (`pid`, `name`) VALUES
(35, 'alberto garcia'),
(36, 'Carlos Munchen'),
(37, 'benjamin Muller'),
(38, 'Toze Bandido'),
(39, 'Peter Parker'),
(40, 'Bruce Wayne'),
(41, 'Logan'),
(42, 'Tony Stark');

到目前为止，我一直没有成功

SELECT * FROM `matches`
    JOIN players ON matches.pid_1 = players.pid OR matches.pid_2 = players.pid
    JOIN decks ON matches.did_1 = decks.did OR matches.did_2 = decks.did
WHERE matches.tid = 2;

SELECT matches.*, players.name, decks.name FROM `matches`, players, decks
WHERE matches.tid = 2 AND matches.pid_1 = players.pid AND matches.pid_2 = players.pid AND matches.did_1 = decks.did AND matches.did_2 = decks.did;

SELECT * FROM `matches`
    RIGHT JOIN players ON matches.pid_1 = players.pid AND matches.pid_2 = players.pid
    RIGHT JOIN decks ON matches.did_1 = decks.did AND matches.did_2 = decks.did
WHERE matches.tid = 2;

Answer 1

尝试：

    SELECT * FROM `matches`
    LEFT JOIN players players1
        ON matches.pid_1 = players1.pid 
    LEFT JOIN players players2
        ON matches.pid_2 = players2.pid 
    LEFT JOIN decks deck1
        ON matches.did_1 = deck1.did 
    LEFT JOIN decks  deck2
        ON matches.did_2 = deck2.did 
    WHERE matches.tid = 2;

Answer 2

您可以通过使用Union尝试如下

SELECT mid,m.result,p1.name as palyer_name,
d1.name as decks_name FROM `matches` m  
left join players p1 on m.pid_1=p1.pid
left join decks d1 on m.did_1=d1.did
union 
SELECT mid,m.result,p2.name,d1.name FROM `matches` m    
left join players p2 on  m.pid_2=p2.pid
left join decks d1 on m.did_2=d1.did

demo fiddle

Answer 3

您不仅应该尝试JOIN，还应该尝试更多限制性输出，例如INNER JOIN（我认为您需要的输出）或LEFT / RIGHT JOIN。

您可以在此Q / A中检查JOIN之间的所有区别： Difference between joins

带JOIN的SQL返回所有组合而不是各自的匹配项

3 个答案: