T-Sql select and group by MIN() - sql

Question

I Have 3 tables like:
ProductCategory [1 - m] Product [1-m] ProductPrice
a simple script like this :
select pc.CategoryId ,pp.LanguageId , pp.ProductId ,pp.Price
from ProductCategory as pc
inner join Product as p on pc.ProductId = p.Id
inner join ProductPrice as pp on p.Id = pp.ProductId
order by CategoryId , LanguageId , ProductId
shows these tabular data :
CategoryId LanguageId ProductId Price
----------- ----------- ----------- ---------------------------------------
1 1 1 55.00
1 1 2 55.00
1 2 1 66.00
1 2 2 42.00
2 1 3 76.00
2 1 4 32.00
2 2 3 89.00
2 2 4 65.00
4 1 4 32.00
4 1 5 77.00
4 2 4 65.00
4 2 5 85.00
now what I need is:
for each category, get full row as is but only with the product that has the minimum price.
I just wrote a simple query that does this like :
with dbData as
(
select pc.CategoryId ,pp.LanguageId , pp.ProductId ,pp.Price
from ProductCategory as pc
inner join Product as p on pc.ProductId = p.Id
inner join ProductPrice as pp on p.Id = pp.ProductId
)
select distinct db1.*
from dbData as db1
inner join dbData as db2 on db1.CategoryId = db2.CategoryId
where db1.LanguageId = db2.LanguageId
and db1.Price = (select Min(Price)
from dbData
where CategoryId = db2.CategoryId
and LanguageId = db2.LanguageId)
and its result is correct:
CategoryId LanguageId ProductId Price
----------- ----------- ----------- ---------------------------------------
1 1 1 55.00
1 1 2 55.00
1 2 2 42.00
2 1 4 32.00
2 2 4 65.00
4 1 4 32.00
4 2 4 65.00
Is there a cooler way for doing this ?
Note: The query must be compliant with Sql-Server 2008 R2+

Answer 1

You could use windowed function like RANK():
WITH cte AS
(
select pc.CategoryId, pp.LanguageId, pp.ProductId, pp.Price,
rnk = RANK() OVER(PARTITION BY pc.CategoryId ,pp.LanguageId ORDER BY pp.Price)
from ProductCategory as pc
join Product as p on pc.ProductId = p.Id
join ProductPrice as pp on p.Id = pp.ProductId
)
SELECT CategoryId, LanguageId, ProductId, Price
FROM cte
WHERE rnk = 1;
LiveDemo

Answer 2

you can add languageid to partition if you need product prices per categoryid and languageid
select top 1 with ties pc.CategoryId ,pp.LanguageId , pp.ProductId ,pp.Price
from ProductCategory as pc
inner join Product as p on pc.ProductId = p.Id
inner join ProductPrice as pp on p.Id = pp.ProductId
order by row_number() over (partition by pc.categoryid order by price)

Answer 3

You are not using the Product table in your query, so it doesn't seem necessary. I would right this as:
select ppc.*
from (select pc.CategoryId, pp.LanguageId , pp.ProductId, pp.Price,
row_number() over (partition by pc.CategoryId order by pp.Price) as seqnum
from ProductCategory pc inner join
ProductPrice pp
on pc.ProductId = pp.ProductId
) ppc
where seqnum = 1
order by CategoryId, LanguageId, ProductId;