Function to Calculate Median in SQL Server

Question

According to MSDN, Median is not available as an aggregate function in Transact-SQL. However, I would like to find out whether it is possible to create this functionality (u

Answer 1

Using a single statement - One way is to use ROW_NUMBER() and filter using sub-query. Here is to find the median salary:

SELECT AVG(a.Salary) FROM                                                             
(SELECT ROW_NUMBER() OVER(ORDER BY Salary) as row_no, Salary FROM Employee)a
CROSS JOIN
(SELECT (COUNT(*)+1)*0.5 AS row_half FROM Employee )t
WHERE a.row_no IN (FLOOR(t.row_half),CEILING(t.row_half))

I have seen similar solutions over the net using FLOOR and CEILING but tried to use a single statement.