Question

我目前使用这种方法来提出一个百分比：

declare @height table
(
    UserId int,
    tall bit
)
insert into @height
select  1, 1 union all
select  2, 1 union all 
select 6, 0 union all
select  3, 0 union all 
select 7, 0 union all
select  4, 1 union all 
select 8, 0 union all
select  5, 0

declare @all decimal(8,5)

select 
    @all = count(distinct UserId)
from @height

select 
    count(distinct UserId) / @all Pct
from @height
where tall = 1

结果：0.375000000

有更好的表现方式吗？如您所见@height

表被击中两次。

谢谢！

Answer 1

这使您只能敲击一次表，并为给定的数据集提供相同的结果。

declare @height table
(
    UserId int,
    tall bit
)
insert into @height
select  1, 1 union all
select  2, 1 union all 
select 6, 0 union all
select  3, 0 union all 
select 7, 0 union all
select  4, 1 union all 
select 8, 0 union all
select  5, 0


select SUM(convert(decimal(8,5), tall)) / convert(decimal(8,5), COUNT(*)) Pct
from @height

根据您的要求，这可能适用于重复的用户ID。至少它会产生与你相同的结果。

select SUM(convert(decimal(8,5), tall)) / convert(decimal(8,5), COUNT(distinct userid)) Pct
from 
    (select distinct UserId, tall
    from @height) t

Answer 2

以下是产生预期结果的替代查询。我不知道这个查询的性能与其他查询相比如何，但我怀疑你可以很容易地测试它。

declare @height table
(
    UserId int,
    tall bit
)
insert into @height
select  1, 1 union all
select  2, 1 union all 
select  4, 1 union all 

select  3, 0 union all 
select  5, 0 union all
select  6, 0 union all
select  7, 0 union all
select  8, 0

Select 1.0 * Count(Distinct Case When Tall = 1 Then UserId End) 
       / Count(Distinct UserId)
From   @height

更快地计算百分比？

2 个答案: