SQL Server 组合行和列答案

【问题标题】：SQL Server combine rows and columnsSQL Server 组合行和列
【发布时间】：2019-07-03 17:59:16
【问题描述】：

请帮忙，我开始学习 sql，我必须将所有 3 位作者组合在一行中。

如何删除 dups 并只显示一个结果？

    with cte_authors (titleID, Authors, lvl)
    as
    (select distinct titles.title_id, convert(nvarchar(max), au_fname + ' ' + au_lname) as Authors , 1 as lvl 
from  titles inner join 
titleauthor on titles.title_id = titleauthor.title_id inner join
authors on titleauthor.au_id = authors.au_id
where au_ord > 2 
    union all   
    select titleauthor.title_id, Authors + '\' + au_fname + ' ' + au_lname , lvl + 1 
        from titleauthor inner join 
             cte_authors on cte_authors.titleID = titleauthor.title_id inner join
             titles on titles.title_id = cte_authors.titleID inner join


             authors on authors.au_id = titleauthor.au_id
                where lvl< 3)

    Select * from cte_authors
    group by titleID, Authors, lvl
    order by lvl

结果：

titleID               Authors                           lvl
TC7777  Burt Gringlesby                                 1
TC7777  Burt Gringlesby\Akiko Yokomoto                  2
TC7777  Burt Gringlesby\Burt Gringlesby                 2
TC7777  Burt Gringlesby\Michael O'Leary                 2
TC7777  Burt Gringlesby\Akiko Yokomoto\Akiko Yokomoto   3
TC7777  Burt Gringlesby\Akiko Yokomoto\Burt Gringlesby  3
TC7777  Burt Gringlesby\Akiko Yokomoto\Michael O'Leary  3
TC7777  Burt Gringlesby\Burt Gringlesby\Akiko Yokomoto  3
TC7777  Burt Gringlesby\Burt Gringlesby\Burt Gringlesby 3
TC7777  Burt Gringlesby\Burt Gringlesby\Michael O'Leary 3
TC7777  Burt Gringlesby\Michael O'Leary\Akiko Yokomoto  3
TC7777  Burt Gringlesby\Michael O'Leary\Burt Gringlesby 3
TC7777  Burt Gringlesby\Michael O'Leary\Michael O'Leary 3

我需要的结果：

titleID               Authors                           lvl
TC7777  Burt Gringlesby\Michael O'Leary\Akiko Yokomoto  3

【问题讨论】：

非图片请分享文本样本数据和预期输出
共享。请帮帮我，谢谢！
你的预期结果是什么
对于给您带来的不便，我深表歉意。我添加了所需的结果
“如何删除 dups”呢？我没有在结果集中看到重复项。

标签： sql-server union common-table-expression union-all

【解决方案1】：

如果您只需要一行包含所有作者的串联字符串，则不需要 CTE。

SELECT titles.title_id, 
    STUFF((
            SELECT '\' + a.au_fname + ' ' + a.au_lname 
            FROM dbo.titleauthor ta 
            INNER JOIN dbo.authors a ON a.au_id = ta.au_id 
            WHERE ta.title_id = titles.title_id 
            ORDER BY ta.au_ord DESC
            FOR XML PATH('')
        ), 1, 1, '') AS Authors,
    (SELECT MAX(au_ord) FROM dbo.titleauthor WHERE title_id = titles.title_id) lvl
FROM titles

title_id    Authors                                         lvl
TC7777      Burt Gringlesby\Michael O'Leary\Akiko Yokomoto  3

【讨论】：