MySQL SUM of LIMIT(3) rows with GROUP BY

Question

Good people, need a bit of a help with MySQL. Tried few solutions online but could get it right.

I have this simple table.

name    amount
john  | 150
john  | 100
john  | 100
john  | 150
jack  | 300
jack  | 100
jack  | 100

Basically, I have to get the users that have sum of 500 in at least 3 rows(ordered by the highest amount). The correct answer should only return jack because only he has sum of 500 in 3 records(ordered by highest). Where else john has 500 in total sum, 3 of his highest amounts would only return 400(150+150+100), so the query doesn't return john .

SELECT 
*,
SUM(amount) as sums
FROM (SELECT * FROM transfer GROUP BY name ORDER BY amount DESC LIMIT 3) as ttl
GROUP BY name
HAVING sums >= 500

It works fine(no errors at least), but the second select(the one inside the bracket) only returns the first row.

Any help is highly appreciated.

Answer 1

Let me assuming that you have another column that is a unique id. Then you can do this as:

select distinct t1.name
from transfer t1 left join
     transfer t2
     on t1.name = t2.name and t1.id < t2.id left join
     transfer t3
     on t1.name = t3.name and t2.id < t3.id
where t1.amount + coalesce(t2.amount, 0) + coalesce(t3.amount, 0) >= 500;

This is not wildly efficient for larger tables. For that, use variables to enumerate the values:

select name
from (select t.*,
             (@rn := if(@n = name, @rn + 1,
                        if(@n := name, 1, 1)
                       )
             ) as rn
      from transfer cross join
           (select @n := '', @rn := 0) params
      order by name, amount desc
     ) t
where rn <= 3
group by name
having sum(amount) >= 500;

This also has the benefit that it does not rely on an id column.