如何连接来自同一个表的数据点？

Question

所以我是 MySQL 新手。我创建了一个数据库，它是我的藏书。它有标题、类型、卷和书的类型（漫画、轻小说、普通小说等）。到目前为止，这是我创建数据库和添加数据的代码。

create database books;
use books;
create table books_in_my_possession (title varchar(100), genre varchar(100), volume varchar (100));
insert into books_in_my_possession (title, genre, volume) values ('Assassins Creed Blade of Shao Jun', 'Historical Fiction', '1');
insert into books_in_my_possession (title, genre, volume) values ('Assassins Creed Blade of Shao Jun', 'Historical Fiction', '2');
insert into books_in_my_possession (title, genre,volume) values ('Torture Princess: Fremd Torturchen', 'Isekai', '1');
insert into books_in_my_possession (title, genre, volume) values ('Torture Princess: Fremd Torturchen', 'Dark Fantasy', '1');
alter table books_in_my_possession
add column book_type varchar(100);
update books_in_my_possession
set book_type = 'manga' 
where title = 'Assassins Creed Blade of Shao Jun';
update books_in_my_possession
set book_type = 'light novel'
where title = 'Torture Princess: Fremd Torturchen';

我想做的是按流派将“Torture Princess: Fremd Torturchen”和“1”（同名）结合起来，这样它就有了“Isekai”和“Dark Fantasy”。我本可以在其中一条价值线中写出“Isekai/Dark Fantasy”或“Isekai, Dark Fantasy”，但我希望它们被视为独立的，因为书籍有多种类型。

我该怎么做呢？

Answer 1

我认为您正在尝试使用group_concat:https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html#function_group-concat

select  title,
        GROUP_CONCAT (genre) as genre,
        volume,
        book_type 
from books.books_in_my_possession
group by title,volume,book_type ;

演示：https://www.db-fiddle.com/f/7yUJcuMJPncBBnrExKbzYz/121