MYSQL：基于第二张表的加入、计数和排名

Question

I have two tables I'm working with in MySQL v5.5.33: members & member_points

Structured as follows:

members :

  id  Name
  1   John    
  2   Jane      

member_points :

  id  id_from  id_to
  1      1       2
  2      2       1
  3      2       1

I was able to get this far, but unable to finish the last 3 columns and rank/sort properly

 id  name  total_sent  total_received  sent_minus_received  rank
 1   John      1                                
 2   Jane      2                               

This is my current code, which I was able to achieve the above.

SELECT *
     , a.id
     , COUNT(m.id) AS id_from_count
  FROM members AS a
  LEFT 
  JOIN member_points AS m 
    ON a.id = m.id_from
 GROUP 
    BY a.id

However the result I'm looking to achieve, includes total received, the variance or difference between sent and received, and lastly ranked based on the difference.

 id  name  total_sent  total_received  sent_minus_received  rank
 2   Jane      2            1                 1               1
 1   John      1            2                -1               2 

Any guidance would be much appreciated.

Thank you for your time.

Answer 1

SELECT m.id, 
       m.name,
       SUM(m.id = mp.id_from) total_sent,
       SUM(m.id = mp.id_to) total_received,
       SUM(m.id = mp.id_from) - SUM(m.id = mp.id_to) `var(sent-received)`,
       DENSE_RANK() OVER ( ORDER BY {unclear from question text} ) `rank`
FROM members m
CROSS JOIN member_points mp
GROUP BY m.id, 
         m.name

Currently using Version 5... My apologies. localhost currently on 5.5.33

SELECT subquery.*, 
       @rank := @rank + 1 `rank`
FROM (SELECT m.id, 
             m.name,
             SUM(m.id = mp.id_from) total_sent,
             SUM(m.id = mp.id_to) total_received,
             SUM(m.id = mp.id_from) - SUM(m.id = mp.id_to) `var(sent-received)`
      FROM members m
      CROSS JOIN member_points mp
      GROUP BY m.id, 
               m.name) subquery, 
     (SELECT @rank := 0) variable
ORDER BY `var(sent-received)` DESC;

fiddle

Answer 2

If you are running MySQL 8.0, you can join, aggregate, and rank with window functions:

select
    m.id,
    m.name,
    sum(m.id = mp.id_from) total_sent,
    sum(m.id = mp.id_to) total_recieved,
    sum(m.id = mp.id_from) - sum(m.id = mp.id_to) diff,
    rank() over(order by sum(m.id = mp.id_from) - sum(m.id = mp.id_to)) rnk
from members as m
left join member_points mp as mp on m.id in (mp.id_from, mp.id_to)
group by m.id, m.name
order by diff desc