Question

我有以下架构，并希望执行一个查询，为articles表中的每个条目返回一行，并在content表中显示相应的content列，以及每个文章标记的列，例如您可以使用concat。

查询应该只选择与某个标记匹配的行。因此，如果提供了标记atdi，则结果集将类似于：

id    content                                                tags
1     on my way nails broke and fell                         song,atdi,invalid
3     im all alone so far up here and my oxygen is all gone  song,atdi,hourglass
4     you know your insides true better than i do            song,atdi,starslight

我已经尝试了几种不同的子查询方式，但不断出现错误 - 这非常令人沮丧。

这是架构：

CREATE TABLE articles (
id int not null default 0,
published datetime,
author int not null default 0,
primary key (id)
);

INSERT INTO articles
(id, published, author)
VALUES
(1, CURRENT_TIMESTAMP, 1),
(2, CURRENT_TIMESTAMP, 1),
(3, CURRENT_TIMESTAMP, 1),
(4, CURRENT_TIMESTAMP, 1);

CREATE TABLE content (
id int not null default 0,
content varchar(250) not null default '',
primary key (id)
);

INSERT INTO content
(id,content)
VALUES
(1,'on my way nails broke and fell'),
(2,'exo skeleton junction at the railroad delayed'),
(3,'im all alone so far up here and my oxygen is all gone'),
(4,'you know your insides true better than i do');

CREATE TABLE tags (
id int not null default 0,
tag varchar(100) not null default '',
primary key (id,tag)
);

INSERT INTO tags
(id,tag)
VALUES
(1,"song"),
(2,"song"),
(3,"song"),
(4,"song"),
(1,"atdi"),
(2,"mars"),
(3,"atdi"),
(4,"atdi"),
(1,"invalid"),
(2,"roulette"),
(3,"hourglass"),
(4,"starslight");

Answer 1

尝试类似这样的事情

select a.id, a.content, b.tags_1 
from content as a  inner join (
    select id, GROUP_CONCAT(tag SEPARATOR ',') as tags_1 FROM tags group by id
) as b on a.id = b.id 
INNER JOIN tags AS c ON a.id = c.id
WHERE c.tag = 'atdi'

使用GROUP_CONCAT()方法

聚合连接表导致MySQL 5上的SQL SELECT

1 个答案: