Question

为这些人找到最“热门”的粉丝。有人拥有的粉丝越多，越多他们是“受欢迎的”。

我需要SQL查询来选择最受欢迎的关注者。

我的表 - （粉丝）

id | person_id | follower_person_id
1    1            2
2    1            3
3    2            1
4    2            4
5    3            1
6    3            2
7    3            4
8    4            3

Person_id 1共有2个关注者（person_id 2，person_id 3），person_id   2有2个粉丝（person_id 1，person_id 4），person_id 3有   共3个粉丝（person_id 1，person_id 2，person_id 4）和person_id   4总共有1位粉丝（person_id 3）。

因此，person_id 3是person_id 1最受欢迎的关注者，   person_id 1是person_id 2，person_id 1（或者）的最受欢迎的关注者   person_id 2）是person_id 3和person_id 3最受欢迎的关注者   是person_id 4最受欢迎。

这是查询...

SELECT t1.person_id, t1.follower_person_id, t2.cnt
FROM followers AS t1
JOIN (
   SELECT person_id, COUNT(*) AS cnt
   FROM followers
   GROUP BY person_id 
) AS t2  ON t1.follower_person_id = t2.person_id
WHERE t1.person_id = 1
ORDER BY t2.cnt DESC LIMIT 1

以上查询输出

person_id, follower_person_id, cnt
-----------------------------------
1,         3,                  3

Here is explanation of above query

此查询仅适用于查找特定人员的热门人物我希望找到一个与所有人最“流行”的追随者配对。

SO输出应该像

person_id, follower_person_id, cnt
-----------------------------------
1,         3,                  3
2,         1,                  2
3,         1,                  2
4,         3,                  3

现在我有了另一个person table

id | name 
1    John         
2    Ali         
3    Rohn         
4    Veronica

现在我想将此ID转换为人名。

最终输出应该像
一样

person_name, follower_person_name, cnt
--------------------------------------
John,        Rohn,                 3
Ali,         John,                 2
Rohn,        John,                 2
Veronica,    Rohn,                 3

我需要sql查询来获取这些数据。

Answer 1

您可以使用以下查询：

SELECT person_name, follower_name, cnt
FROM (
   SELECT person_name, follower_name, cnt,
          @rn := IF(@pname = person_name, @rn + 1,
                    IF(@pname := person_name, 1, 1)) AS rn
   FROM (
      SELECT t3.name AS person_name, t4.name AS follower_name, t2.cnt
      FROM followers AS t1
      JOIN (
         SELECT person_id, COUNT(*) AS cnt
         FROM followers
         GROUP BY person_id 
      ) AS t2  ON t1.follower_person_id = t2.person_id
      JOIN person AS t3 ON t1.person_id = t3.id
      JOIN person AS t4 ON t1.follower_person_id = t4.id   
   ) AS x
   CROSS JOIN (SELECT @rn := 0, @pname := '') AS vars
   ORDER BY person_name, cnt DESC) AS v
wHERE v.rn = 1;

<强>输出：

person_name follower_name   cnt
--------------------------------
John        Rohn            3
Veronica    Rohn            3
Ali         John            2
Rohn        Ali             2

查询使用变量以获得每组最大记录。

Demo here

Answer 2

SELECT p1.name, p2.name, t2.cnt
FROM followers AS t1
JOIN (
   SELECT person_id, COUNT(*) AS cnt
   FROM followers
   GROUP BY person_id 
) AS t2  ON t1.follower_person_id = t2.person_id
join person p1 on t1.person_id=person.id
join person p2 on t1.follower_person_id=person.id
ORDER BY t2.cnt DESC LIMIT 1

Answer 3

也许您可以将它与您选择的语言上的一些代码结合起来尝试使用以下查询从高到低对关注者进行排序，并获取第二列的名称：

select f.person_id, p.name
from followers f 
inner join person p on p.id=f.person_id
group by f.person_id order by count(f.follower_person_id) desc

对于每个输出ID（让我们称之为FIXED_ID_FROM_PREVIOUS_QUERY，你试着让他跟随的人并创建第1和第3列

select p.name, count(f.follower_person_id)
from followers f 
inner join person p on p.id=f.person_id 
inner join person pf on pf.id=f.follower_person_id where 
f.person_id in (select person_id from followers where follower_person_id=FIXED_ID_FROM_PREVIOUS_QUERY)
group by f.person_id order by count(f.follower_person_id) desc

返回所有用户的列表，与最“热门”的关注者配对。有人拥有的粉丝越多，他们就越“受欢迎”

3 个答案: