具有多个联接的SQL分组错误地合并了结果

Question

嗨，我在查询查询合并记录时遇到了麻烦。

我有两个表Authors和Publications，它们与Publication ID之间存在多对多关系。 因为每个作者可以有很多出版物，每个出版物也有很多作者。 我希望我的查询返回一组作者的每个出版物，并将对出版物有贡献的其他每个作者的ID归入一个字段。 （我正在使用mySQL）

我试图在下面以图形方式显示它

    Table: authors               Table:publications
AuthorID | PublicationID        PublicationID | PublicationName
    1    |   123                       123    |       A
    1    |   456                       456    |       B
    2    |   123                       789    |       C
    2    |   789
    3    |   123
    3    |   456

我希望我的结果集如下

 AuthorID | PublicationID | PublicationName | AllAuthors
     1    |       123     |        A        |    1,2,3
     1    |       456     |        B        |    1,3
     2    |       123     |        A        |    1,2,3
     2    |       789     |        C        |     2
     3    |       123     |        A        |    1,2,3
     3    |       456     |        B        |    1,3

这是我的查询

Select   Author1.AuthorID,
    Publications.PublicationID,
    Publications.PubName,
    GROUP_CONCAT(TRIM(Author2.AuthorID)ORDER BY Author2.AuthorID ASC)AS 'AuthorsAll'
FROM Authors AS Author1
LEFT JOIN Authors AS Author2
ON Author1.PublicationID = Author2.PublicationID
INNER JOIN Publications
ON Author1.PublicationID = Publications.PublicationID
WHERE Author1.AuthorID ="1" OR Author1.AuthorID ="2" OR Author1.AuthorID ="3" 
GROUP BY Author2.PublicationID

但是它返回以下内容

 AuthorID | PublicationID | PublicationName | AllAuthors
     1    |       123     |        A        |    1,1,1,2,2,2,3,3,3
     1    |       456     |        B        |    1,1,3,3
     2    |       789     |        C        |     2

当where语句中只有一个AuhorID时，它将提供所需的输出。 我一直无法弄清楚，有人知道我要去哪里了吗？

Answer 1

要消除重复的作者，请更改：

ON Author1.PublicationID = Author2.PublicationID

至：

ON Author1.PublicationID = Author2.PublicationID AND
   Author1.AuthorID <> Author2.AuthorID

另外，更改：

GROUP BY Author2.PublicationID

至：

GROUP BY Author1.AuthorID, Author2.PublicationID

Answer 2

我想我不确定您为什么首先需要GROUP BY。 您为什么不能像这样使用相关子查询：

Select   Author1.AuthorID
    ,  Publications.PublicationID
    , Publications.PubName
    , (
        Select GROUP_CONCAT(TRIM(Author2.AuthorID) ORDER BY Author2.AuthorID ASC) 
        From Authors As Author2
        Where Author2.PublicationID = Publications.PublicationID
        ) AS 'AuthorsAll'
FROM Authors AS Author1
    INNER JOIN Publications
        ON Author1.PublicationID = Publications.PublicationID
Where Author1.AuthorId In("1","2","3")