How to find median in sql

Question

I have the following sql query which gives me the total h_time grouped by month, week and day. Instead I want the median h_time for month, week and day. How do I do that in Orac

Answer 1

The problem isn't the median() function, it's the group by column.

Oracle DATE datatype is actually a DATETIME, e.g. 2017-05-24 08:09:11. So when comparing dates we have to take the time element into consideration.

The easiest way to do this is by truncating the date value, which sets the time to midnight. So in your case that would look like this:

SELECT trunc(day) as DAY,
       MEDIAN(H_TIME) AS H_TIME
FROM (
    ...
)
group by trunc(day)

This solution is better than using to_char() to remove the time element because the datatype remains DATE. So if you sort the results order by trunc(day) you get the expected calendar order, whereas sorting on to_char(day) would give an unexpected alphanumeric ordering.