SQL Selecting dates with maximum sale for each department [duplicate] - sql

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Closed 3 years ago.
I am troubled with writing a tricky query.
I have the following table:
For each department I want to print date with largest profit;
I tried coming up with such a query myself:
Select DISTINCT(Name), Date_sale, MAX(A) as B FROM (SELECT
Departments.Name, SALES.Date_sale, SUM(GOODS.Price * SALES.Quantity)
AS A FROM DEPARTMENTS, GOODS, SALES
WHERE DEPARTMENTS.Dept_id = GOODS.Dept_id AND GOODS.Good_id =
SALES.Good_id GROUP BY DEPARTMENTs.Name, SALES.Date_sale)
GROUP BY Name, Date_sale;
But the problem it that departments are printed several times because I groupped by both name and date.
How should I fix it?

Answer 1

You can try below way-
with cte as
(
SELECT
Departments.Name, SALES.Date_sale, SUM(GOODS.Price * SALES.Quantity)
AS profit FROM DEPARTMENTS inner join GOODS on DEPARTMENTS.Dept_id = GOODS.Dept_id
inner join SALES on GOODS.Good_id = SALES.Good_id
GROUP BY DEPARTMENTs.Name, SALES.Date_sale
)A
select * from cte a
where profit =
(select max(profit) from cte b on a.department=b.department)
OR you can use row_number()
select * from
(
select *, row_number() over(partition by department oder by profit desc) as rn
from cte
)A where rn=1

Answer 2

You can write it using ROW_NUMBER which will give a number to each date's total count grouped by the department as following and then you can take the highest sale date using rn = 1
SELECT NAME, DATE_SALE, A
FROM
(
SELECT
DEPARTMENTS.NAME, SALES.DATE_SALE,
ROW_NUMBER() OVER(
PARTITION BY DEPARTMENTS.NAME
ORDER BY SUM(GOODS.PRICE * SALES.QUANTITY) DESC NULLS LAST
) AS RN,
SUM(GOODS.PRICE * SALES.QUANTITY) AS A
FROM DEPARTMENTS
JOIN GOODS ON ( DEPARTMENTS.DEPT_ID = GOODS.DEPT_ID )
JOIN SALES ON ( GOODS.GOOD_ID = SALES.GOOD_ID )
GROUP BY DEPARTMENTS.NAME,
SALES.DATE_SALE
)
WHERE RN = 1;
Important, Use the standard ANSI-joins.
Cheers!!

Answer 3

i would use join-s here as it is needed to pull info from 2 tables linked via the third table.
Something like this (but I have not tested this query, just suggesting an approach):
Select department.name as dept, MAX(sales.quantity) as max_sales, sales.date_sale
from goods
Left outer join departments on departments.dept_id = goods.dept_id
Left outer join sales on sales.good_id = goods.good_id
Group by dept