MySQL：从同一个表中选择同名的两列[重复]答案

【问题标题】：MySQL: select two column from the same table with the same name [duplicate]MySQL：从同一个表中选择同名的两列[重复]
【发布时间】：2023-04-08 00:06:01
【问题描述】：

我正在创建一个应用程序来管理 game 和 team 数据。这是 mySQL 数据库结构：

CREATE TABLE team (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL,
    PRIMARY KEY (id)
);

CREATE TABLE game (
    id INT NOT NULL AUTO_INCREMENT,
    id_team_A INT NOT NULL,
    id_team_B INT NOT NULL,
    PRIMARY KEY (id)
);

-- TEST VALUES: --

INSERT INTO team VALUES
    (1, "Barcelona"),
    (2, "Milan"),
    (3, "Real Madrid"),
    (4, "Inter");

INSERT INTO game VALUES
    (1, 1, 3),
    (2, 2, 4);

如您所见，每个 match 都有 2 个不同的 team 关联。

我正在尝试（没有成功）进入单个查询匹配 id、团队 A 名称、团队 B 名称。

首先我尝试了这样的查询：

SELECT game.id, team.name, team.name
FROM team INNER JOIN game
ON game.id_team_A = team.id;

但我的查询不关心 match.id_team_B 并且重复的 match.name 字段不会解决问题。

然后我开始使用嵌套在一起的选择查询：

SELECT @g_id := game.id as id,
(SELECT team.name FROM team INNER JOIN game ON game.id_team_A = team.id WHERE game.id = @g_id) AS team_A,
(SELECT team.name FROM team INNER JOIN game ON game.id_team_B = team.id WHERE game.id = @g_id) AS team_B
FROM game;

最后我得到了我想要的：

+-----+---------------+---------------+
| id  |    team_A     |    team_B     |
+-----+---------------+---------------+
|  1  |   Barcelona   |  Real Madrid  |
+-----+---------------+---------------+
|  2  |     Milan     |     Inter     |
+-----+---------------+---------------+

是否有更简单/更快/更酷的查询来获得相同的结果？

注意：SQL Fiddle

【问题讨论】：

标签： mysql inner-join

【解决方案1】：

你需要两个别名：

SELECT g.id, t1.name team_A, t2.name team_B
FROM game g, team t1, team t2
WHERE g.id_team_A = t1.id AND g.id_team_B = t2.id

或加入：

SELECT g.id, t1.name team_A, t2.name team_B
FROM game g JOIN team t1 ON g.id_team_A = t1.id
JOIN team t2 ON g.id_team_B = t2.id

【讨论】：

其实一个别名就可以了，这样就不会有名字冲突了

【解决方案2】：

你可以在同一个表之间进行连接，所以你可以这样做：

SELECT g.id as id, a.name as team_a, b.name as team_b 
FROM team a INNER JOIN game g ON g.id_team_A = a.id
INNER JOIN team b ON g.id_team_B = b.id

【讨论】：