Finding Median in Sql Server - sql

Question

I want to get the median of unitRate from [dbo].[ReplaceCost_DirectCost_Details] view in Microsoft Sql Server Management Studio. I already got Min,Max and avg of it.But do not know about median. I tried following code, but did not get median .Thanks in advacen for your help.
select
JobName as JobName
,Client as Client
,AssetClass as AssetClass
,AssetType as AssetType
,AssetSubType as AssetSubType
,Component as Component
,ComponentType as ComponentType
,ComponentSubType as ComponentSubType
,UnitRate AS UnitRate
,Max(UnitRate) over (partition by JobName,Client,AssetClass,AssetType,AssetSubType,Component,ComponentType,ComponentSubType) as [MaxFinalUnitRate]
,Min(UnitRate) over (partition by JobName,Client,AssetClass,AssetType,AssetSubType,Component,ComponentType,ComponentSubType) as [MinFinalUnitRate]
,AVG(UnitRate) over (partition by JobName,Client,AssetClass,AssetType,AssetSubType,Component,ComponentType,ComponentSubType) as [MeanFinalUnitRate]
,AVG (UnitRate) over (partition by JobName,Client,AssetClass,AssetType,AssetSubType,Component,ComponentType,ComponentSubType)as Median
from
(
Select top (10)
JobName as JobName
,Client as Client
,AssetClass as AssetClass
,AssetType as AssetType
,AssetSubType as AssetSubType
,Component as Component
,ComponentType as ComponentType
,ComponentSubType as ComponentSubType
,UnitRate AS UnitRate
,ROW_NUMBER () over (partition by JobName,Client,AssetClass,AssetType,AssetSubType,Component,ComponentType,ComponentSubType order by UnitRate) as [RowNum]
,COUNT(*) OVER (PARTITION BY JobName,Client,AssetClass,AssetType,AssetSubType,Component,ComponentType,ComponentSubType ) AS RowCnt
from [dbo].[ReplaceCost_DirectCost_Details] rdd
where client = 'APV_Ballina_Shire_Council_Old' and UnitRate is not Null and UnitRate <> 0
) x
WHERE RowNum IN ((RowCnt + 1) / 2, (RowCnt + 2) / 2)

Answer 1

EDIT
SQL Fiddle
CREATE TABLE Table1
([somevalue] int)
;
INSERT INTO Table1
([somevalue])
VALUES
(141),
(325),
(325),
(353),
(3166),
(325),
(207),
(141),
(3166),
(161)
;
Query 1:
with cte as (
select *
, row_number() over(order by somevalue) as RowNum
, count(*) over() as RowCnt
from table1
)
select
*
from CTE
WHERE RowNum IN ((RowCnt + 1) / 2, (RowCnt + 2) / 2)
| somevalue | RowNum | RowCnt |
|-----------|--------|--------|
| 325 | 5 | 10 |
| 325 | 6 | 10 |
Please consider the following small example. There are 7 rows of data, the median is the "midpoint" of those, so the where clause uses a row number compared to row count, and returns just that midpoint valuse. That value (67) repesents the median of that small sample.
SQL Fiddle
MS SQL Server 2014 Schema Setup:
CREATE TABLE Table1
([somevalue] int)
;
INSERT INTO Table1
([somevalue])
VALUES
(2),
(45),
(67),
(89),
(4567),
(6),
(1290)
;
Query 1:
with cte as (
select *
, row_number() over(order by somevalue) as RowNum
, count(*) over() as RowCnt
from table1
)
select
*
from CTE
WHERE RowNum IN ((RowCnt + 1) / 2, (RowCnt + 2) / 2)
Results:
| somevalue | RowNum | RowCnt |
|-----------|--------|--------|
| 67 | 4 | 7 |

Answer 2

(sorry for using a second answer, but it will get lost if just added to the earlier one)
I am really not certain what the expected output of your query is. But I note that you are using TOP(10) and for that to work you must have an order by otherwise the result is indeterminate for the first 10 rows.
While the following may produce many more rows than you need, perhaps it will help lead to a solution.
WITH Basis as (
SELECT
JobName
, Client
, AssetClass
, AssetType
, AssetSubType
, Component
, ComponentType
, ComponentSubType
, UnitRate
, ROW_NUMBER() OVER (PARTITION BY JobName, Client, AssetClass, AssetType, AssetSubType, Component, ComponentType, ComponentSubType
ORDER BY UnitRate)
AS [rownum]
FROM [dbo].[ReplaceCost_DirectCost_Details] rdd
WHERE client = 'APV_Ballina_Shire_Council_Old'
AND UnitRate IS NOT NULL
AND UnitRate <> 0
)
, Top10s as (
SELECT
JobName
, Client
, AssetClass
, AssetType
, AssetSubType
, Component
, ComponentType
, ComponentSubType
, UnitRate
, rownum
, COUNT(*) OVER (PARTITION BY JobName, Client, AssetClass, AssetType, AssetSubType, Component, ComponentType, ComponentSubType)
AS rowcnt
FROM Basis
WHERE rownum <= 10
)
, Medians as (
SELECT
JobName
, Client
, AssetClass
, AssetType
, AssetSubType
, Component
, ComponentType
, ComponentSubType
, AVG(UnitRate) AS Median
FROM Top10s
WHERE RowNum IN ((RowCnt + 1) / 2, (RowCnt + 2) / 2)
GROUP BY
JobName
, Client
, AssetClass
, AssetType
, AssetSubType
, Component
, ComponentType
, ComponentSubType
, AVG(UnitRate)
)
SELECT
JobName
, Client
, AssetClass
, AssetType
, AssetSubType
, Component
, ComponentType
, ComponentSubType
, UnitRate
, rownum
, rowcnt
, MAX(UnitRate) OVER (PARTITION BY JobName, Client, AssetClass, AssetType, AssetSubType, Component, ComponentType, ComponentSubType) AS [maxfinalunitrate]
, MIN(UnitRate) OVER (PARTITION BY JobName, Client, AssetClass, AssetType, AssetSubType, Component, ComponentType, ComponentSubType) AS [minfinalunitrate]
, AVG(UnitRate) OVER (PARTITION BY JobName, Client, AssetClass, AssetType, AssetSubType, Component, ComponentType, ComponentSubType) AS [meanfinalunitrate]
, Medians.Median
FROM Top10s t
JOIN Medians m ON t.JobName = m.JobName
AND t.Client = m.Client
AND t.AssetClass = m.AssetClass
AND t.AssetType = m.AssetType
AND t.AssetSubType = m.AssetSubType
AND t.Component = m.Component
AND t.ComponentType = m.ComponentType
AND t.ComponentSubType = m.ComponentSubType
;