在SELECT

Question

我有一些看起来像这样的表：

CREATE TABLE Games (
    Id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
    Title VARCHAR(100) NOT NULL
);

CREATE TABLE Tags(
    Id INTEGER NOT NULL AUTO_INCREMENT PRIMARY KEY,
    Tag VARCHAR(30) NOT NULL
);

CREATE TABLE GamesTags(
    GameId INTEGER NOT NULL,
    TagId INTEGER NOT NULL,
    PRIMARY KEY (GameId, TagId),
    FOREIGN KEY(GameId) REFERENCES Games(Id),
    FOREIGN KEY(TagId) REFERENCES Tags(Id)
);

如何创建一个SELECT查询，该查询可以在一列中输出游戏的标题，而在另一列中用逗号分隔所有标记。例如：

Title       | Tags                |
-----------------------------------
Fortnite    | survival, action    |
Super Mario | platform, adventure |

Answer 1

SELECT 
   A.Title, 
   GROUP_CONCAT(DISTINCT C.Tag ORDER BY C.Tag ASC SEPARATOR ',') Tags
FROM Games A 
LEFT JOIN GameTags B
ON A.Id=B.GameID
LEFT JOIN Tags C
ON B.TagId=C.Id
GROUP BY A.Title;

有关见解，请参阅：

MySQL Group By

MySQL Join Made Easy For Beginners

MySQL GROUP_CONCAT Function