如何计算Mysql中一行的中位数？

Question

I am new to sql and have been struggling about nan-median, for example, I have a table with three (million) rows, each with ten numbers (or null):

row1: 1,2,3,null,4,5,6,7,8,9
----------
row2: 2,4,null,6,8,2,1,0,9,10
----------
row3: 1,1,1,1,null,7,2,9,9,9
----------

How to get the nan-median of each row ?

Answer 1

According to your question, If you have 10 columns that you want to calculate. The trick is to avoid the null values with Coalesce function. Use this logic:

Select (coalesce(Col1, 0) + coalesce(Col2, 0) + coalesce(Col3, 0)+ coalesce(Col4, 0)+coalesce(Col5, 0)+coalesce(Col6, 0)+coalesce(Col7, 0)+coalesce(Col8, 0)+coalesce(Col9, 0)+.coalesce(Col10, 0))/10 
from yourtable

Answer 2

select(
   (select MAX(cols) from 
    (select TOP 50 PERCENT cols from table ORDER BY cols) )  
        + 
          (select MIN(cols) from 
            (select TOP 50 PERCENT cols from table ORDER BY cols DESC) ) 
     ) / 2  
Median

Select max of first 50% rows by sorting the rows in asc which should be the median in case if column count is even. Select min of next 50% rows by ordering the rows in desc, in case if column count is even, this will be median or else max of (firsthalf+min of secondhalf)/2 will be the median.