Calculate variable of max amount in a group

问题

I have difficulties in doing the following exercise. I would need to find how frequent is that an id is not the max_id in the group with the most amount. This should be done considering groups that contain at least two different people. Data comes from two different tables: max_id comes from table1 (I will call it a)as well as user and amount; id comes from table2 (b) as well as group. From the text above, the conditions should be

(1) a.id<>b.max_id /* is not */
(2) people in group >=2
(3) a.id<> id of max amount

The dataset looks like

(a)

max_id  user  amount

(b)

group email

From a previous exercise, I had to compute distinct people as follows:

sel a.distinct users
a.max_id
b.id
from table1 as a
inner join table2 as b
on b.id=a.max_id

where
b.max_id is not null
and b.time is null

No information from amount was required in the exercise above. This is the main difference between the two exercises, but the structure and fields are quite similar. Now, I would need to edit the code above in order to find how frequent is that an id is not the max_id in the group with the most amount. This makes sense only if groups have at least two different persons/users. I think I will need to join tables to get the id of max amount in a group and count people in a group, but I do not know how to do it. Any help would be greatly appreciated. Thank you.

Data sample

max_id  user  amount id group email
12       1    -2000  12 house email1
312      1      0    54 work  email1
11       32    -213  11 house email32
41       13    -43   78 work  email13
312      53    -650  34 work  email53
1        67    -532  43 defense email67
64       76   -9650  98 work  email76

For my understanding, what the exercise asks and based on the code above, I should find values for id<>max_id and having more than 2 users in a group (i.e. house, work, defence). Then, what I would need to select is id <> id of max amount.

I hope this it can be a bit more clear.

回答1:

assuming yoy have a query as

select t.User, m.Email, m.Model, m.Amount
from my_table m
inner join   (
    select user, max(amount) max_amount
    from my_table 
    group by user
) t on t.user = m.user
    and t.max_amount  = m.amount

you can obatin the max di for each amoun using

select max(id), Amount
from (

    select m.id, t.User, m.Email, m.Model, m.Amount
    from my_table m
    inner join   (
        select user, max(amount) max_amount
        from my_table 
        group by user
    ) t on t.user = m.user
        and t.max_amount  = m.amount
) k

and you should obtain the valud of id that are not equal to max id as

select mm.id, t.User, mm.Email, mm.Model, mm.Amount
    from my_table mm
    inner join   (
        select user, max(amount) max_amount
        from my_table 
        group by user
    ) t on t.user = m.user
        and t.max_amount  = m.amount
inner join  (
    select max(k.id) max_id, k.Amount
    from (

        select m.id, t.User, m.Email, m.Model, m.Amount
        from my_table m
        inner join   (
            select user, max(amount) max_amount
            from my_table 
            group by user
        ) t on t.user = m.user
            and t.max_amount  = m.amount
    ) k

    ) kk ON kk.max_id <> mm.id

来源：https://stackoverflow.com/questions/61823394/calculate-variable-of-max-amount-in-a-group

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sql

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