可能是一个新手问题,但我希望根据数据库总大小将我们的服务器库存分成几个大小均匀的组,并且很难弄清楚如何对它们进行分组。我认为 NTILE 可能会起作用,但我就是无法将注意力集中在平均分配组上。我下面的示例只是随机订购服务器。我希望结果是大小相当均匀的 3 组(显然不准确)。
使用 SQL Server 2012。感谢任何帮助。谢谢。
declare @Servers table (ServerName sysname, TotalSizeGB decimal (12,2))
insert into @Servers values
('Server1',123.45),
('Server2',234.56),
('Server3',345.67),
('Server4',456.78),
('Server5',567.89),
('Server6',678.90),
('Server7',789.01),
('Server8',890.12),
('Server9',901.23),
('Server10',1023.35)
select GroupNumber, sum(TotalSizeGB) as TotalSizeGB
from (
select ServerName, sum(TotalSizeGB) as TotalSizeGB, ntile(3) over (order by newid()) as GroupNumber
from (
select ServerName, TotalSizeGB from @Servers
) x
group by ServerName
) y
group by GroupNumber
这里的预期输出是三组,每组约 2000GB。我预计它不会很准确,但至少很接近。如果按服务器分组,则可能如下所示:
ServerName TotalSizeGB GroupNumber
Server10 1023.35 1
Server1 123.45 1
Server5 567.89 1
Server3 345.67 1
Server4 456.78 2
Server7 789.01 2
Server6 678.90 2
Server2 234.56 3
Server9 901.23 3
Server8 890.12 3
如果我按每组计算总和,则结果将如下所示:
GroupNumber TotalSizeGB
1 2060.36
2 1924.69
3 2025.91
最佳答案
SELECT *
FROM(
SELECT y.TotalSizeGB,
CASE
WHEN y.AnotherGrp%2=0 AND y.PseudoGrpNumber=0 THEN 2
WHEN y.AnotherGrp%2=0 AND y.PseudoGrpNumber=1 THEN 1
WHEN y.AnotherGrp%2=0 AND y.PseudoGrpNumber=2 THEN 0
ELSE y.PseudoGrpNumber
END GrpNumber
FROM(
SELECT
x.ServerName,
x.TotalSizeGB,
(2+ROW_NUMBER() OVER(ORDER BY x.TotalSizeGB DESC))%3 PseudoGrpNumber,
(2+ROW_NUMBER() OVER(ORDER BY x.TotalSizeGB DESC))/3 AnotherGrp,
ROW_NUMBER() OVER(ORDER BY x.TotalSizeGB DESC) RowNum
FROM @Servers x
)y
)z
PIVOT( SUM(z.TotalSizeGB) FOR z.GrpNumber IN([0],[1],[2]) ) pvt;
结果:
0 1 2
------- ------- -------
2048.02 1925.80 2037.14
一些解释:
这个想法是对 TotalSizeGB
列上的数据进行降序排序。然后,每 3 个连续行首先按 AnotherGrp
顺序分组在一起(列 DESC
),然后按 ASC
顺序分组在一起(列 PseudoGroNumber
和 GrpNumber
)。如果执行SELECT * FROM () y
派生表那么结果将是:
ServerName TotalSizeGB PseudoGrpNumber AnotherGrp GrpNumber RowNum
---------- ------------ --------------- ---------- --------- ------
Server10 1023.35 0 1 0 1
Server9 901.23 1 1 1 2
Server8 890.12 2 1 2 3
Server7 789.01 0 2 2 4
Server6 678.90 1 2 1 5
Server5 567.89 2 2 0 6
Server4 456.78 0 3 0 7
Server3 345.67 1 3 1 8
Server2 234.56 2 3 2 9
Server1 123.45 0 4 2 10
关于sql-server - 根据聚合创建大小均匀的组,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17889830/