Calculating the Median with Mysql

Question

I\'m having trouble with calculating the median of a list of values, not the average.

I found this article Simple way to calculate median with MySQL

It has a

Answer 1

Finding median in mysql using group_concat

Query:

SELECT
    IF(count%2=1,
       SUBSTRING_INDEX(substring_index(data_str,",",pos),",",-1),
       (SUBSTRING_INDEX(substring_index(data_str,",",pos),",",-1) 
         + SUBSTRING_INDEX(substring_index(data_str,",",pos+1),",",-1))/2) 
    as median 
FROM (SELECT group_concat(val order by val) data_str,
      CEILING(count(*)/2) pos,
      count(*) as count from data)temp;

Explanation:

Sorting is done using order by inside group_concat function

Position(pos) and Total number of elements (count) is identified. CEILING to identify position helps us to use substring_index function in the below steps.

Based on count, even or odd number of values is decided.

• Odd values: Directly choose the element belonging to the pos using substring_index.
• Even values: Find the element belonging to the pos and pos+1, then add them and divide by 2 to get the median.

Finally the median is calculated.