Mysql 选择所有多对多关系

鉴于下表：

author
--------------
id int(11)
name varchar

author_type
---------------
id int(11)
type varchar

author_has_type
---------------
author_id int(11)
author_type_id int(11)

我正在尝试编写一个查询，它执行以下操作：

给定作者类型，它将显示以下内容

author.name           types
-The authors name-    -All types of the author-

现在，我尝试使用的查询是

Select author.name, GROUP_CONCAT(author_type.type) as types
from author
left join author_has_type on author.id = author_has_type.author_id
left join author_type on author_has_type.author_type_id = author_type.id
where author_type.type = "EXAMPLE TYPE"

---

但是，当我这样做时，它只返回组_concat中的给定类型。我理解为什么会发生这种情况，但有没有办法获取该作者的每种类型？

您需要一个

分组依据

，并删除

where

子句：

Select a.name, GROUP_CONCAT(t.type) as types
from author a left join
     author_has_type aht
     on a.id = aht.author_id left join
     author_type t
     on aht.author_type_id = t.id
group by a.name;

编辑：

我想你想要的是：

Select a.name, GROUP_CONCAT(t.type) as types
from author a left join
     author_has_type aht
     on a.id = aht.author_id left join
     author_type t
     on aht.author_type_id = t.id
group by a.name
having max(author_type.type = 'EXAMPLE TYPE') > 0;

---

您需要将分组添加到查询中。为了限制要输出的行，请使用have和子查询

SELECT author.name, GROUP_CONCAT(author_type.type) as types
FROM author
LEFT JOIN author_has_type on author.id = author_has_type.author_id
LEFT JOIN author_type on author_has_type.author_type_id = author_type.id
GROUP BY (author.name)
HAVING author.id IN (
    SELECT id FROM author 
    JOIN author_has_type ON author.id = author_has_type.author_id
    JOIN author_type ON author_has_type.author_type_id = author_type.id
    WHERE author_type.type = "EXAMPLE TYPE"
)

添加两个内部联接以筛选到要查找的类型上。然后使用接下来的两个连接获取作者的所有类型

将查询分组并将其放入子查询中。在外部查询中，使用结果将authordata加入到结果中

---

是的，但这只会得到所有作者及其类型。我希望获得所有作者及其所有类型，在where子句中具有指定的类型。@user2827048。你的问题澄清了这个问题。请参阅我的编辑。

SELECT author.name, 
       GROUP_CONCAT(author_type.type) as types
  FROM author
  LEFT JOIN author_has_type on author.id = author_has_type.author_id
  LEFT JOIN author_type on author_has_type.author_type_id = author_type.id
       (SELECT author.ID 
         FROM author
         LEFT JOIN author_has_type on author.id = author_has_type.author_id
         LEFT JOIN author_type on author_has_type.author_type_id = author_type.id
        WHERE author_type.type = "EXAMPLE TYPE") temp
    ON author.id=temp.id

SELECT 
    author.name, 
    result.types 
FROM (
    SELECT author.id, GROUP_CONCAT(types.type) AS types
    FROM 
        author
    INNER JOIN author_has_type
        ON author.id = author_has_type.author_id
    INNER JOIN author_type 
        ON author_has_type.author_type_id = author_type.id 
        AND author_type.type = "funny"
    INNER JOIN author_has_type AS has_types
        ON author.id = has_types.author_id
    INNER JOIN author_type AS types
        ON has_types.author_type_id = types.id 
    GROUP BY author.id
) AS result 
INNER JOIN author 
    USING(id)