如何在 Presto DB 中使用范围

Question

我想使用 PrestoDB found for SQL Server 执行以下操作？

select t.range as 'latency', count(*) as 'Total'
from (
  select case  
    when latency between 0 and 0.250 then 'Fast'
    when latency between 0.250 and 1.0 then 'Normal'
    when latency between 1.0 and 2.0 then 'Elevated'
    else 'High' 
  end as range
  from myprestodb.mytable) t
group by t.range

...所以我得到这样的结果：

latency        | Total
-------------------------------------
   Fast        |        11
   Normal      |        14
   Elevated    |         3
   High        |         1

Answer 1

你可以试试：

select range as Latency, count(*) as Total
from (
  select case  
    when latency > 0 and latency <= 0.250 then 'Fast'
    when latency > 0.250 and latency <= 1.0 then 'Normal'
    when latency > 1.0 and latency <= 2.0 then 'Elevated'
    else 'High' 
  end as range
  from myprestodb.mytable
)
group by range

Answer 2

您可以使用 count_if 为每列计算的内容提供条件。这正是我要找的：

select count_if(latency < 0.25) as "Fast: < .25", 
    count_if(latency > 0.25 and latency <= 1.0) as "Normal: .25 - 1", 
    count_if(latency > 1.0 and latency <= 2.0) as "Elevated: 1 - 2", 
    count_if(latency > 2.0) as "High: > 2"

from myprestodb.mytable
...

如何在 Presto DB 中使用范围

How do I use ranges with Presto DB

presto