Simple way to calculate median with MySQL

Question

What\'s the simplest (and hopefully not too slow) way to calculate the median with MySQL? I\'ve used AVG(x) for finding the mean, but I\'m having a hard time fi

Answer 1

Most of the solutions above work only for one field of the table, you might need to get the median (50th percentile) for many fields on the query.

I use this:

SELECT CAST(SUBSTRING_INDEX(SUBSTRING_INDEX(
 GROUP_CONCAT(field_name ORDER BY field_name SEPARATOR ','),
  ',', 50/100 * COUNT(*) + 1), ',', -1) AS DECIMAL) AS `Median`
FROM table_name;

You can replace the "50" in example above to any percentile, is very efficient.

Just make sure you have enough memory for the GROUP_CONCAT, you can change it with:

SET group_concat_max_len = 10485760; #10MB max length

More details: http://web.performancerasta.com/metrics-tips-calculating-95th-99th-or-any-percentile-with-single-mysql-query/