Question

我想在数据库中选择每对两列，但只选择价格最低的条目。因此，我想输出id和price列。

但它不起作用：

我的表：

id | category | type | name | price
1;"car";"pkw";"honda";1000.00
2;"car";"pkw";"bmw";2000.00

SQL：

select min(price) price, id
from cartable
group by category, type

结果： Column "cartable.id" must be present in GROUP-BY clause or used in an aggregate function.

Answer 1

如果您想要价格最低的条目，请计算最低价格并将信息重新加入：

select ct.*
from cartable ct join
     (select category, type, min(price) as price
      from cartable
      group by category, type
     ) ctp
     on ct.category = ctp.category and ct.type = ctp.type and ct.price = ctp.price;

Answer 2

您可以使用EXISTS子句实现此目的：

SELECT * 
FROM  cartable ct 
WHERE 
  NOT EXISTS (
           SELECT * 
           FROM  cartable 
           WHERE ct.type = type and ct.category = categoery and ct.price < price)

对于速度比较，你可以试试这个：

SELECT DISTINCT ON (type, category), id, price
FROM cartable
ORDER BY price DESC

Answer 3

SELECT id, price
from  cartable C
inner join
(
select min(price) as price , category, type
from cartable
group by category, type
)T
on T.category = C.category
and T.type = C.type

Answer 4

大多数时候，除了决定使用Select - Over

之外，您无能为力

select price, id
from(
    select price, id, [rnk] = ROW_NUMBER() over( partition by category, type order by price)
    from cartable
) as a
where [rnk]=1

适当地创建索引，并且性能良好。

在您的示例中，如下所示：

CREATE NONCLUSTERED INDEX [foo]
ON [dbo].[cartable] ([category],[type])
INCLUDE ([price])

Answer 5

也许您可以尝试：

select id, price from cartable 
where price = (select min(price) from cartable);

如何选择每组最低价格的记录

5 个答案: