Execute the following SQL Server T-SQL script in SSMS Query Editor to demonstrate the calculation of statistical median. For an odd number set, it produces unique value. For even number set, one has to decide.

-- SQL Server statistical calculation - median - median is different from average

USE AdventureWorks2008;
 
WITH cteOrderQty
     AS (SELECT DISTINCT OrderQty
         FROM   Sales.SalesOrderDetail)
SELECT   MedianOrderQty = a.OrderQty
FROM     cteOrderQty a
         CROSS JOIN cteOrderQty b
GROUP BY a.OrderQty
HAVING   SUM(CASE
               WHEN b.OrderQty <= a.OrderQty THEN 1
               ELSE 0
             END) >= (COUNT(* )) / 2
         AND SUM(CASE
                   WHEN b.OrderQty >= a.OrderQty THEN 1
                   ELSE 0
                 END) >= (COUNT(* ) / 2)
/*
MedianOrderQty
21
22
20

*/