sql - T-Sql 按 MIN() 选择和分组

Question

我有 3 个表:

ProductCategory [1 - m] Product [1-m] ProductPrice

像这样的简单脚本:

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

显示这些表格数据:

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

现在我需要的是:对于每个类别，按原样获取整行，但仅包含具有最低价格的产品。

我刚刚写了一个简单的查询，就像这样:

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)

它的结果是正确的:

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

有没有更酷的方法来做到这一点？

注意:查询必须符合Sql-Server 2008 R2+

Answer 1

你可以使用像RANK() 这样的窗口函数:

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