与大多数朋友一起前5名

Question

嗨，我是SQL的新手，我正在试图弄清楚我将如何与大多数朋友（userId）获得前5名“乐队”，这就是我所拥有的;一个usertbl用userId作为PK然后是带有bandId作为PK的bandsTbl然后我有一个带有FK userId和bandId的表bandfriends。

bandfriends
userid | bandId
---------------
 1     | 1
 1     | 2
 1     | 3

谢谢！

Answer 1

SELECT TOP 5 bandId, fanCount
FROM 
    (SELECT bandId, COUNT(*) as fanCount
     FROM bandfriends
     GROUP BY bandId
     ORDER BY COUNT(*) DESC)

您也可以选择在select语句中指定WITH TIES。请参阅this和this。

Answer 2

select top 5 b.b_name, count(friends) as numOfFriends 
from bands b inner join link l on b.b_id = l.bands inner join
friends f on f.f_id = l.friends 
group by b.b_name 
order by numOfFriends desc

如果你有朋友表，乐队表和链接表，对我有用：）

Answer 3

在mysql.org上阅读COUNT和GROUP BY

你会想要这样的东西（我还没有测试过）：

SELECT bandId, COUNT(*) as fans FROM bandfriends
ORDER BY fans DESC
GROUP BY bandId
LIMIT 5;