根据MSDN, Median在Transact-SQL中不能作为聚合函数使用。但是,我想知道是否可以创建此功能(使用create Aggregate函数、用户定义函数或其他方法)。
最好的方法(如果可能的话)是什么——允许在聚合查询中计算中值(假设是数值数据类型)?
根据MSDN, Median在Transact-SQL中不能作为聚合函数使用。但是,我想知道是否可以创建此功能(使用create Aggregate函数、用户定义函数或其他方法)。
最好的方法(如果可能的话)是什么——允许在聚合查询中计算中值(假设是数值数据类型)?
当前回答
使用一条语句——一种方法是使用ROW_NUMBER(), COUNT()窗口函数并过滤子查询。下面是薪资中位数:
SELECT AVG(e_salary)
FROM
(SELECT
ROW_NUMBER() OVER(ORDER BY e_salary) as row_no,
e_salary,
(COUNT(*) OVER()+1)*0.5 AS row_half
FROM Employee) t
WHERE row_no IN (FLOOR(row_half),CEILING(row_half))
我在网上看到过类似的解决方案,使用地板和天花板,但尝试使用单一的语句。(编辑)
其他回答
使用一条语句——一种方法是使用ROW_NUMBER(), COUNT()窗口函数并过滤子查询。下面是薪资中位数:
SELECT AVG(e_salary)
FROM
(SELECT
ROW_NUMBER() OVER(ORDER BY e_salary) as row_no,
e_salary,
(COUNT(*) OVER()+1)*0.5 AS row_half
FROM Employee) t
WHERE row_no IN (FLOOR(row_half),CEILING(row_half))
我在网上看到过类似的解决方案,使用地板和天花板,但尝试使用单一的语句。(编辑)
对于连续变量/测量'table1'中的'col1'
select col1
from
(select top 50 percent col1,
ROW_NUMBER() OVER(ORDER BY col1 ASC) AS Rowa,
ROW_NUMBER() OVER(ORDER BY col1 DESC) AS Rowd
from table1 ) tmp
where tmp.Rowa = tmp.Rowd
以下是我的解决方案:
with tempa as
(
select value,row_number() over (order by value) as Rn,/* Assigning a
row_number */
count(value) over () as Cnt /*Taking total count of the values */
from numbers
where value is not null /* Excluding the null values */
),
tempb as
(
/* Since we don't know whether the number of rows is odd or even, we shall
consider both the scenarios */
select round(cnt/2) as Ref from tempa where mod(cnt,2)=1
union all
select round(cnt/2) a Ref from tempa where mod(cnt,2)=0
union all
select round(cnt/2) + 1 as Ref from tempa where mod(cnt,2)=0
)
select avg(value) as Median_Value
from tempa where rn in
( select Ref from tempb);
从员工表中得到工资的中位数
with cte as (select salary, ROW_NUMBER() over (order by salary asc) as num from employees)
select avg(salary) from cte where num in ((select (count(*)+1)/2 from employees), (select (count(*)+2)/2 from employees));
试试下面的逻辑来找出中位数:
考虑一个包含以下数字的表格: 1、1、2、3、4、5所示
中位数是2.5
with tempa as
(
select num,count(num) over() as Cnt,
row_number() over (order by num) as Rnum
from temp),
tempb as
(
select round(cnt/2) as ref_value
from tempa where mod(cnt,2)<>0
union all
select round(cnt/2) from tempa where mod(cnt,2)=0
union all
select round(cnt/2+1)
from tempa where mod(cnt,2)=0
)
select avg(num) from tempa
where rnum in (select * from tempb);