Query to Show Max Sales for Each Seller - sql

Question

I have a table like this (sample):
Name_Seller Month Value
---------------------------
Seller A Jan 200
Seller B Jan 100
Seller A Fev 300
Seller B Fev 100
Seller C Jan 400
Seller A Mar 200
Seller D Jan 300
SQL query:
SELECT Name_Seller, Month, Value
FROM SALES
WHERE Value = (SELECT MAX(Value) FROM SALES GROUP BY Name_Seller);
And I'd like to print for each seller which was his maximum sale and when it was.
Could you help me fix my query and explain why it does not work?
I tried:
select name_seller, month, max(value)
from sales
group by name_seller, month;
but this query returns:
+---------------+------------+------+
| NAME_SELLER | MAX(VALUE) | MONTH|
+---------------+------------+------+
| SELLER A | 4182.00 | Jan |
| SELLER A | 3261.00 | Fev |
| SELLER A | 4219.00 | Mar |
| SELLER B | 2123.00 | Jan |
| SELLER B | 2111.00 | Fev |
| SELLER B | 3918.00 | Mar |
| SELLER C | 3000.00 | Jan |
| SELLER C | 4000.00 | Fev |
| SELLER C | 1500.00 | Mar |
| SELLER D | 2819.00 | Jan |
| SELLER D | 3881.00 | Fev |
| SELLER D | 2012.00 | Mar |
+---------------+------------+------+
And I would like just THE TOP sale of each salesman and when it was.
So it should return just one sale for each salesman.

Answer 1

With ROW_NUMBER() window function:
SELECT t.Name_Seller, t.Month, t.Value
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY Name_Seller ORDER BY Value DESC) rn
FROM SALES
) t
WHERE t.rn = 1
Change ROW_NUMBER() with RANK() if you want ties returned.
Or with a correlated subquery in the WHERE clause:
SELECT s.* FROM SALES s
WHERE s.Value = (SELECT MAX(VALUE) FROM SALES WHERE Name_Seller = s.Name_Seller)
Or if your database supports it:
SELECT * FROM SALES
WHERE (Name_Seller, Value) IN (SELECT Name_Seller, MAX(VALUE) FROM SALES GROUP BY Name_Seller)

Answer 2

You query can also bring the results however the "=" operator in where clause needs to change to "IN" because the query below brings more than 1 row so it needs a IN operator in where clause. Also, the data you have in your query returned the correct results but please be wary to use it in general because it will also bring wrong results because of comparison with sales amount( value) as example given by #forpas.
When changed the operator, your query will work.
SELECT Name_Seller, Month, Value FROM SALES
WHERE Value IN (Select MAX(Value) FROM SALES GROUP BY Name_Seller);
You can also use the rank() window function
SELECT Name_Seller, Month, VALUE
FROM (SELECT Name_Seller, Month, VALUE,
RANK() OVER (PARTITION BY Name_Seller ORDER BY VALUE DESC ) as RN
FROM SALES
) A
WHERE A.RN = 1

Answer 3

It will look like this:
SELECT Name_Seller, Month, MAX(Value)
FROM SALES
GROUP BY Name_Seller, Month;

Answer 4

You can use below query,
select name_seller, month, max(value) from sales group by name_seller, month;
If you are expecting month as well then use,
select s2.name_seller, s1.month, max(s2.value) from sales s1
inner join
(select name_seller, max(value) as value from sales
group by name_seller) s2
on (s1.name_seller = s2.name_seller and s1.value = s2.value);