sql - Mysql多对多查询

Question

我的 mysql 数据库中设置了多对多表。团队可以参加多场比赛，每场比赛有 2 支球队。它们之间有一个名为 teams_games 的表。 SHOW CREATE TABLE 信息如下。

我已经弄乱了这个查询有一段时间了。此时我不关心它是否需要子查询、连接或联合。我已经尝试了所有这些，但没有一个是令人满意的，我想我错过了一些东西。我一直遇到的断开连接是从每场比赛中找到两个团队 ID，然后使用 tid 获取团队信息。

我想做的是，如果给定一个游戏 ID (gid)，我可以查询以找到:

home_team_name, home_team_id, away_team_name, away_team_id, team_league(客场和主场是同一个联赛), games表的所有信息

Table Create Table

<pre><code> teams CREATE TABLE `teams` ( `tid` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(60) NOT NULL, `league` varchar(2) NOT NULL, `active` tinyint(1) NOT NULL, PRIMARY KEY (`tid`) </code></pre>

)

CREATE TABLE <code>teams_games</code> (

<pre><code>`tid` int(10) unsigned NOT NULL, `gid` int(10) unsigned NOT NULL, `homeoraway` tinyint(1) NOT NULL, PRIMARY KEY (`tid`,`gid`), KEY `gid` (`gid`), CONSTRAINT `teams_games_ibfk_1` FOREIGN KEY (`tid`) REFERENCES `teams` (`tid`), CONSTRAINT `teams_games_ibfk_2` FOREIGN KEY (`gid`) REFERENCES `games` (`gid`) </code></pre>

)

CREATE TABLE <code>games</code> (

<pre><code>`gid` int(10) unsigned NOT NULL AUTO_INCREMENT, `location` varchar(60) NOT NULL, `time` datetime NOT NULL, `description` varchar(400) NOT NULL, `error` smallint(2) NOT NULL, `home_score` smallint(2) DEFAULT NULL, `away_score` smallint(2) DEFAULT NULL, PRIMARY KEY (`gid`) </code></pre>

)

Answer 1

为什么不直接删除 teams_games 表并更改 games:

CREATE TABLE games (

 `gid` int(10) unsigned NOT NULL AUTO_INCREMENT,
`location` varchar(60) NOT NULL,
`time` datetime NOT NULL,
`description` varchar(400) NOT NULL,
`error` smallint(2) NOT NULL,
`home_score` smallint(2) DEFAULT NULL,
`away_score` smallint(2) DEFAULT NULL,
`home_tid` int(10) unsigned NOT NULL,
`away_tid` int(10) unsigned NOT NULL,
PRIMARY KEY (`gid`)
)

然后你可以像这样写一个简单的连接:

SELECT 
    g.*, 
    h.name as home_team, 
    a.name as away_team, 
    h.league as league 
FROM games AS g 
    INNER JOIN teams AS h ON g.home_tid = h.tid
    INNER JOIN teams as a ON g.away_tid = a.tid
WHERE gid = ?