mysql只对连接查询中的不同值计数 [英] mysql count only for distinct values in joined query

问题描述

哇！这是一个奇怪的标题，但我很高兴你看，因为我找不到另一种方式说。

我有一张人物表格和一张照片和视频链接表。
我加入了人们的媒体，当然一个人可以有多个媒体。

我试图在一个查询中抓住前30个人和他们的所有媒体，但当我说LIMIT 0,30。当然，我只能得到前30个媒体文件，可能是10个人。

在我进行查询之前，我不知道有多少媒体文件人会有。有没有办法我可以说LIMIT DISTINCT（uid 0,30）????

或类似的东西？

解决方案

您可以在您的MySQL版本中使用子查询吗？

 code> select * 
从媒体m 
内部连接
（选择uid 
从users_tbl 
限制0,30）map 
在地图上。 uid = m.uid 
 inner join users_tbl u 
 on u.uid = m.uid 
  

WOW! That's a weird title, but I'm happy you're looking, cause I couldn't find another way to say it.

I have a table of people and a table of links to photos and videos. I join the people to the media, and of course a person can have more than one piece of media.

I am attempting to grab the first 30 people and all of their media in one query, but when I say LIMIT 0,30. Of course I'll only get the first 30 media files, which could be 10 people.

Before I make the query, I don't know how many media files each person is going to have. Is there a way I can say LIMIT DISTINCT(uid 0,30)????

or something like that?

解决方案

Can you use subqueries in your version of MySQL?

select *
from media m
inner join
     ( select uid
     from users_tbl
     limit 0,30) map
  on map.uid = m.uid
inner join users_tbl u
  on u.uid = m.uid

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