Question

我想构建一个查询（或尽可能少）来对数据集进行分组。所以给定了一些桶，我想根据特定的列返回结果。

因此给出了一个名为score的列，它是一个包含以下内容的双精度：

我希望能够将GROUP BY子句与以下函数一起使用：

SELECT MIN（得分），MAX（得分），SUM（得分）FROM表GROUP BY BUCKETS（得分，3）

理想情况下，这将返回3行（将结果分组为3个桶，每个组中的数量尽可能接近相等）：

 90.00, 91.00, 181.00
 94.00, 96.00, 190.00
 98.00, 99.00, 197.00

是否有某些功能可以做到这一点？我想避免返回所有行并自己弄清楚桶段。

戴夫

Answer 1

create table test (
id int not null auto_increment primary key,
val decimal(4,2)
) engine = myisam;

insert into test (val) values 
 (90.00),
 (91.00),
 (94.00),
 (96.00),
 (98.00),
 (99.00);

select min(val) as lower,max(val) as higher,sum(val) as total from (
select id,val,@row:=@row+1 as row
from test,(select @row:=0) as r order by id
) as t
group by ceil(row/2)

+-------+--------+--------+
| lower | higher | total  |
+-------+--------+--------+
| 90.00 |  91.00 | 181.00 |
| 94.00 |  96.00 | 190.00 |
| 98.00 |  99.00 | 197.00 |
+-------+--------+--------+
3 rows in set (0.00 sec)

不幸的是，mysql没有像rownum（）这样的分析函数，所以你必须使用一些变量来模拟它。完成后，您可以简单地使用ceil（）函数，以便根据需要对每个行进行分组。希望尽管我的英语很有帮助。

set @r = (select count(*) from test);
select min(val) as lower,max(val) as higher,sum(val) as total from (
select id,val,@row:=@row+1 as row
from test,(select @row:=0) as r order by id
) as t
group by ceil(row/ceil(@r/3))

或使用单个查询

select min(val) as lower,max(val) as higher,sum(val) as total from (
select id,val,@row:=@row+1 as row,tot
from test,(select count(*) as tot from test) as t2,(select @row:=0) as r order by id
) as t
group by ceil(row/ceil(tot/3))

基于等值列值的查询结果查询

1 个答案: