SQL Server 中位數、標准差、平均數

create table examines
(
    [e_id] [int] IDENTITY(1,1) NOT NULL,
    [dept_name] [nvarchar](200) NULL,
    [ph_score] [int] NULL
)


SELECT
   dept_name,
   AVG(sp) as '中位數'
FROM
(
   SELECT
      dept_name,
      cast(ph_score as decimal(5,2)) sp,
      ROW_NUMBER() OVER (
         PARTITION BY dept_name 
         ORDER BY ph_score ASC, e_id ASC) AS RowAsc,
      ROW_NUMBER() OVER (
         PARTITION BY dept_name 
         ORDER BY ph_score DESC, e_id DESC) AS RowDesc
   FROM examines SOH
) x
WHERE 
   RowAsc IN (RowDesc, RowDesc - 1, RowDesc + 1)
GROUP BY dept_name
ORDER BY dept_name;


select dept_name,STDEV(ph_score) as '標準差' from examines group by dept_name

select dept_name,avg(ph_score) as '平均數' from examines group by dept_name