SQL选择组查询

Question

下面是我的表

表1

+--------+----------+---------+ 
| amount | make  | product | 
+--------+----------+---------+ 
| 100 | Nokia | Mobiles | 
| 300 | Samesung | Mobiles | 
| 700 | Micromax | Mobiles | 
| 1000 | Karbonn | Mobiles | 
| 500 | Lava  | Mobiles | 
| 100 | Floyer | Gift | 
| 500 | Arichies | Gift | 
| 300 | Feeling | Gift | 
+--------+----------+---------+ 

现在我想显示每个产品的两个最高金额...

所以我想建立一个SQL查询这给我的结果如下..

+--------+----------+---------+ 
| amount | make  | product | 
+--------+----------+---------+ 
| 1000 | Karbonn | Mobiles | 
| 700 | Micromax | Mobiles | 
| 500 | Arichies | Gift | 
| 300 | Feeling | Gift | 
+--------+----------+---------+ 

请帮我建立这样的查询..

Answer 1

您可以使用此解决方案来检索基础上，amount的“组间最大”：

SELECT a.* 
FROM Table1 a 
INNER JOIN Table1 b ON a.product = b.product AND a.amount <= b.amount 
GROUP BY a.amount, a.product 
HAVING COUNT(*) <= 2 

简单的改变，不过2很多你想每次检索顶部行产品。

如果你想获取每个产品的最低两行，你可以简单地在INNER JOIN的<=标志更改为>=。

可以摆弄这个解决方案在这里：SQL-Fiddle Demo

Answer 2

select top 2 amount, make, product from table1 
where product='Mobiles' 
order by amount desc 
union 
select top 2 amount, make, product from table1 
where product='Gift' 
order by amount desc 

Answer 3

select product, make, amount, rnk 
from (
    select l.product, l.make, l.amount, count(*) as rnk 
    from table1 as l 
    left join table1 as r 
    on (r.product = l.product and l.amount <= r.amount) 
    group by l.product, l.make 
) a 
where rnk <= 2 

看到IDEEA和其他的例子在这里：http://www.xaprb.com/blog/2005/09/27/simulating-the-sql-row_number-function/

，并根据赞恩边测试数据sql fiddle。

Answer 4

您可以通过两种方式做到这一点： 1）添加行索引列，将反映订单，然后选择与行< = 2

所有行

SELECT amount, make,product 
FROM 
(SELECT ROW_NUMBER() OVER (PARTITION BY [product] ORDER BY [amount] DESC) AS [RowID],* 
FROM [dbo].[Table1]) RESULT 
WHERE RowID <= 2 

2）您也可以加入表本身

SELECT a1.* FROM Table1 AS a1 
    LEFT JOIN Table1 AS a2 
    ON a1.product = a2.product AND a1.amount<= a2.amount 
GROUP BY a1.product 
HAVING COUNT(*) <= 2; 

Answer 5

SELECT a.* 
FROM Table1 a 
INNER JOIN Table1 b ON a.product = b.product AND a.amount <= b.amount 
GROUP BY a.amount, a.product 
HAVING COUNT(*) <= 2 
ORDER BY a.amount desc 

请参阅http://sqlfiddle.com/#!2/9ba82/1