如何获得每年 SQLite 的 x 个最高结果

Question

我的解决方案有问题，我找到了这个例子：

(SELECT COUNT(*) FROM person AS b    
WHERE b.group = a.group AND b.age >= a.age) <= 2    
ORDER BY a.group ASC, a.age DESC

（来自：Get top n records for each group of grouped results）

但我需要在旧列的基础上创建新列，因此我需要进行一些计算，当我尝试添加更多内容时，我收到一条错误消息。如果我简单地添加方程式，就可以了，例如：

(SELECT COUNT(*) FROM person AS b   
WHERE b.group = a.group AND b.age*100 >= a.age*100) <= 2   
ORDER BY a.group ASC, a.age DESC

但是当我尝试重命名我的新专栏时，AS 太多了。

我也尝试过使用 UNION ALL，但我的 SQLite 对 () 不满意。这对我根本不起作用：

(   
  select *     
  from mytable    
  where `year` = 2012   
  order by score*100/50 AS percent desc   
  LIMIT 2   
)   
UNION ALL   
(   
  select *   
  from mytable    
  where `year` = 2013   
  order by score*100/50 AS percent desc   
  LIMIT 2   
)

"Result: near "(": syntax error
At line 1:
("

即使我在 () 之前取出 SELECT 和 FROM，我也会收到错误消息。

select * from mytable   
(where `year` = 2012   
  order by score*100/50 AS percent desc   
  LIMIT 2)   

UNION ALL   

select * from mytable    
(where `year` = 2013   
  order by score*100/50 AS percent desc   
  LIMIT 2)

near "WHERE": syntax error

有人可以解释一下为什么吗？

编辑

这是数据。

| Person | Year  | Score |   
+--------+-------+-------+
| Bob    | 2013  | 32    |   
| Jill   | 2012  | 34    |   
| Shawn  | 2012  | 42    |   
| Jake   | 2012  | 29    |   
| Paul   | 2013  | 36    |   
| Laura  | 2013  | 39    |

想要的结果集：

| Person | Year  | Percent |    
+--------+-------+---------+   
| Shawn  | 2012  | 84      |   
| Jill   | 2012  | 68      |   
| Laura  | 2013  | 78      |   
| Paul   | 2013  | 72      |   
+--------+-------+---------+

其中百分比 = 得分*100/50

Answer 1

此语法应该有效：

select * 
from (
  select *     
  from mytable    
  where `group` = 1   
  order by age desc   
  LIMIT 2   
)   
UNION ALL   
select * 
from (   
  select *   
  from mytable    
  where `group` = 2   
  order by age desc   
  LIMIT 2   
);

但你也可以用 ROW_NUMBER():

select t.`group`, t.age, ....<rest of the columns from mytable> 
from (
  select *, row_number() over (partition by `group` order by age desc) rn
  from mytable
  where `group` in (1, 2)
) t 
where t.rn <= 2

如何获得每年 SQLite 的 x 个最高结果

How to get x top results for each year SQLite

sql

sqlite

variables

greatest-n-per-group

union-all