Bagaimana menemukan median di sql

Coba ganti :

SUM(H_TIME) AS HANDLE_TIME

oleh :

MEDIAN(H_TIME) AS HANDLE_TIME

(baris 3)

EDIT:Untuk bulan, ganti:

select 
MONTH, WEEK, DAY,

Oleh:

select 
MONTH,

Dan:

GROUP BY

MONTH
,WEEK
,DAY

Oleh:

GROUP BY 
MONTH

Selama berminggu-minggu, ganti:

select 
MONTH, WEEK, DAY,

Oleh:

select 
MONTH, WEEK,

Dan:

GROUP BY

MONTH
,WEEK
,DAY

Oleh:

GROUP BY 
MONTH
,WEEK