How can MySQL query the records with the largest consumption amount of each user?

There was a problem during the interview Query the consumption amount of each user Table structure [id, user_id, amount]

I want to :

SELECT    user_id,    max( amount ) FROM    orders GROUP BY    user_id

But I see that many statements given by people in the community use subqueries . Why is it so complicated ？
such as :

SELECT    o.* FROM    orders oRIGHT JOIN (    SELECT        max(amount) mxa,        user_id     FROM        orders     GROUP BY        user_id     ) m ON o.user_id = m.user_id AND o.amount = m.mxa

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Take the answer ：

Because the query fields are different . It's ok if you just check the maximum amount , But if you need to query other relevant information about the order , Your writing is not suitable .
Due to the use of group by grouping . The normal field of the query must be in the group field .

SELECT    o.* FROM    orders oRIGHT JOIN (    SELECT        max(amount) mxa,        user_id     FROM        orders     GROUP BY        user_id     ) m ON o.user_id = m.user_id AND o.amount = m.mxa

This method is aimed at real scenes , Query the order record information corresponding to each user's consumption amount .
The logic of implementation ： The sub query finds the maximum order amount of each user , Then, it is related and matched according to the order amount , Find the corresponding order record .

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