Find Median Given Frequency of Numbers

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- Tag: getmedian, #sql

The Numbers table keeps the value of number and its frequency.

+----------+-------------+ | Number | Frequency | +----------+-------------| | 0 | 7 | | 1 | 1 | | 2 | 3 | | 3 | 1 | +----------+-------------+

In this table, the numbers are 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 3, so the median is (0 + 0) / 2 = 0.

+--------+ | median | +--------| | 0.0000 | +--------+

Write a query to find the median of all numbers and name the result as median.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## https://code.dennyzhang.com/find-median-given-frequency-of-numbers select avg(t3.Number) as median from Numbers as t3 inner join (select t1.Number, abs(sum(case when t1.Number>t2.Number then t2.Frequency else 0 end) - sum(case when t1.Number<t2.Number then t2.Frequency else 0 end)) as count_diff from numbers as t1, numbers as t2 group by t1.Number) as t4 on t3.Number = t4.Number where t3.Frequency>=t4.count_diff