Question

我有一个简单的表Customers和fields id, name, rating, seller_id。查询结果

select seller_id, MAX(rating) 
from Customer 
group by seller_id

是按seller_id分组的客户，其评分的最大值。像这样：

seller_id  rating
2          17
3          20
4          17

如何修改此查询以另外获取客户的ID？如果我将id添加到SELECT我收到错误，我应该添加id分组。但是我想只获得指定id的上面显示的值。有谁知道如何做到这一点？谢谢。

Answer 1

试试这个

select c1.* from Customer c1 inner join 
(select seller_id, MAX(rating) as rating from Customer 
group by seller_id) c2 on c1.rating  = c2.rating

或

 SELECT c1.* FROM Customer b1 LEFT JOIN Customer c2
 ON (b1.seller_id = b2.seller_id  AND b1.rating > b2.br_created_date)
 WHERE b2.rating is null;

Answer 2

尝试：

select t.id, t.seller_id, t.rating
from Customer c
join (
    select seller_id, MAX(rating) rating
    from Customer 
    group by seller_id
) x
on x.seller_id = c.seller_id
and x.rating = c.rating

Answer 3

SimarjeetSingh有一个很好的答案。再调整一下：

select c.customer_id, c.seller_id
from customer c
join (
  select seller_id, max(rating) max_rating
  from customer
  group by seller_id
) s 
  on c.seller_id = s.seller_id
  and c.rating = s.max_rating

这样您就可以比较seller_id和最高评分。

Answer 4

数据集分为使用GROUP BY子句的组。分组属性很常见每个小组成员共享的密钥。分组属性通常是单个属性列但可以是多列或一个不能基于的表达式小组职能。请注意，仅分组属性和组功能是使用时在SELECT子句中允许使用 GROUP BY。

参考这个 Select EMP with max SAL from each DEPT

查询以获得分组结果

4 个答案: