给定一组格式为 {FIXED PREFIX}/{NUMERIC ID}/... 的 URL，如何检索具有最高 {NUMERIC ID} 的 URL？

Question

我想查询包含艺术家姓名和相应的封面视频，这是 Link 列中的最高 ID。在此示例中，第二行带有 ..embd/125/... link 格式永远不会改变。我正在使用 PHP ,MySQL 和 innodb engine

我首先对这两个表进行了 INNER JOIN：

Id | Artist
1    John Doe
2    Jane Doe

还有这个

Id | Id_Artist | Link 
53   1           http://example.com/embd/123/video/...
54   1           http://example.com/embd/125/video/...
55   1           http://example.com/embd/124/video/...   
56   1           http://example.com/embd/122/video/... 
57   2           http://example.com/embd/128/video/...
58   2           http://example.com/embd/129/video/...    
59   2           http://example.com/embd/130/video/...

输出所有艺术家的预期结果，他们是视频

SELECT fp.id, fp.name, gl.link AS Video
FROM feed_post_artist AS fp
INNER JOIN gallery gl ON gl.id_artist = fp.id

Id | Id_Artist | Link 
 1   John Doe    http://example.com/embd/123/video/...
 1   John Doe    http://example.com/embd/125/video/...
 1   John Doe    http://example.com/embd/124/video/...   
 1   John Doe    http://example.com/embd/122/video/... 
 2   Jane Doe    http://example.com/embd/128/video/...
 2   Jane Doe    http://example.com/embd/129/video/...    
 2   Jane Doe    http://example.com/embd/130/video/...

是否可以使用正则表达式来比较每个艺术家的视频，并且 return 只比较最高的 link id 作为结果？（前4行125最高，后3行130最高）。我试过使用 MAX() 但它显然不起作用。

Id | Id_Artist | Link 
 1   John Doe    http://example.com/embd/125/video/...
 2   Jane Doe    http://example.com/embd/130/video/...

编辑：

正如朱利安在评论中所建议的那样，MySQL SUBSTR() 解决了这个特殊情况。但是，当 id 超过 999 时，它将停止工作。

SELECT fp.id, fp.name, SUBSTR(gl.link,28,5) AS Video
FROM feed_post_artist AS fp
INNER JOIN gallery gl ON gl.id_artist = fp.id

唯一缺少的部分是将结果分组到 return 只有 MAX()

Answer 1

如果公共部分始终相同并且数字的长度也相同，您可以简单地通过

获得字符串组的最大值

  SELECT fp.id, fp.name, gl.link AS Video
  FROM feed_post_artist AS fp
  INNER JOIN gallery gl ON gl.id_artist = fp.id
  where ( gl.artist_id,gl.link)  in 
        ( select artist_id,  max(link) ) 
           from feed_post_artist 
           group by artist_id )

否则您可以替换公共部分 http://example.com/embd/123/video/... 并在下一个 / 之前获取字符串部分有了这个你应该得到你需要的号码

substr( replace(link, 'http://example.com/embd/' , '' ), 
    locate(replace(link, 'http://example.com/embd/' , '' ), '/', 1))

所以你可以使用一个元组来匹配由 artist_id 分组的数字的最大值，正确地转换为 int

  SELECT fp.id, fp.name, gl.link AS Video
  FROM feed_post_artist AS fp
  INNER JOIN gallery gl ON gl.id_artist = fp.id
  where ( gl.artist_id, 
      cast(  substr( replace(link, 'http://example.com/embd/' , '' ), 
    locate(replace(link, 'http://example.com/embd/' , '' ), '/', 1)) ) AS UNSIGNED)  in 
        ( select artist_id, 
           max(   CAST(substr( replace(link, 'http://example.com/embd/' , '' ), 
              locate(replace(link, 'http://example.com/embd/' , '' ), '/', 1)) 
          ) AS UNSIGNED)
           from feed_post_artist 
           group by artist_id )

Answer 2

select      a.Id
           ,a.Artist
           ,g.Link

from                    feed_post_artist    as a

            left join  (select      Id_Artist
                                   ,substr(max(concat(lpad(substring_index(substring_index(Link,'/',5),'/',-1),10,'0'),Link)),11)   as Link  

                        from        gallery as g

                        group by    Id_Artist
                        ) g

            on          g.Id_Artist =
                        a.Id

order by    a.Id

+----+----------+---------------------------------------+
| Id | Artist   | Link                                  |
+----+----------+---------------------------------------+
| 1  | John Doe | http://example.com/embd/125/video/... |
+----+----------+---------------------------------------+
| 2  | Jane Doe | http://example.com/embd/130/video/... |
+----+----------+---------------------------------------+

给定一组格式为 {FIXED PREFIX}/{NUMERIC ID}/... 的 URL，如何检索具有最高 {NUMERIC ID} 的 URL？

Given a set of URL in the format {FIXED PREFIX}/{NUMERIC ID}/..., how to retrieve the URL with the highest {NUMERIC ID}?

php

regex

mysql

sql

innodb