Function to Calculate Median in SQL Server

sql-server tsql aggregate-functions median
Yaakov Ellis picture Yaakov Ellis · Aug 27, 2009 · Viewed 471.2k times · Source

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 (using the Create Aggregate function, user defined function, or some other method).

What would be the best way (if possible) to do this - allow for the calculation of a median value (assuming a numeric data type) in an aggregate query?

Answer

Jeff Atwood picture Jeff Atwood · Jan 8, 2010

If you're using SQL 2005 or better this is a nice, simple-ish median calculation for a single column in a table:

SELECT
(
 (SELECT MAX(Score) FROM
   (SELECT TOP 50 PERCENT Score FROM Posts ORDER BY Score) AS BottomHalf)
 +
 (SELECT MIN(Score) FROM
   (SELECT TOP 50 PERCENT Score FROM Posts ORDER BY Score DESC) AS TopHalf)
) / 2 AS Median

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