SQL: Group by - further attribute with largest quantity - mysql

Question

I'm new to SQL and facing following problem:
This is my table:
name city people
-----|-----|--------|
John | A | 5 |
Ben | D | 6 |
John | A | 5 |
Ben | A | 5 |
John | B | 8 |
Ben | D | 6 |
I want to group by the name and receive associated to the name that city with the largest quantity. As a second query, instead of the largest quantity, that city with the highest sum of inhabitants.
This would be the outcome for the first query:
name city
-----|-----|
John | A |
Ben | D |
Thank you!

Answer 1

I don't know exactly what you mean by "to the name that city with the largest quantity". What I understood was you sum the column 'people' per couple (name, city), thus (John, A) would be 10 and (John, B) would be 8, and you take the max value to get (John, A).
In this case, you can do it this way:
SELECT
name,
city
FROM
(SELECT
name,
city,
SUM(people) AS tot
FROM table
GROUP BY name, city
ORDER BY name ASC, tot DESC) AS a
GROUP BY name ;
As for the city with the largest number of inhabitants, you just have to group by city and sum the column people and take the max:
SELECT
city,
SUM(people) AS nb_inhabitants
FROM table
GROUP BY city
ORDER BY nb_inhabitants DESC
LIMIT 1;

Answer 2

SELECT name, city, sum( people )
FROM `detail`
GROUP BY name
ORDER BY people ASC
LIMIT 0 , 30
I am not really understand what your are expecting ,but I guess you want to do this thing.
Description : I am group by people from there name , and got sum of the people and make them ASC order. I am not sure your are expect this thing.
You can also , group people by their city
SELECT name, city, sum( people )
FROM `detail`
GROUP BY city
ORDER BY people ASC
LIMIT 0 , 30
If this not you expect , Please , further describe question ,we will try to give some answer.

Answer 3

Try this, I have tried by making a table as per your sample data,
CREATE TABLE KaiTable
(
NAME VARCHAR(50)
,city CHAR(1)
,people INT
);
INSERT INTO KaiTable
VALUES
(
'John'
,'A'
,5
),
('Ben ' ,'D' ,6),
('John' ,'A' ,5),
('Ben ' ,'A' ,5) ,
('John' ,'B' ,8) ,
('Ben ' ,'D' ,6)
SELECT NAME,city
FROM
(SELECT NAME,city,SUM(people) AS PeopleSum
FROM KaiTable
GROUP BY NAME, city
ORDER BY NAME ASC, PeopleSum DESC) AS a
GROUP BY NAME DESC;
SQL Fiddle Demo