How to compute a median in PrestoSQL?

Question

It seems like there is no native function for that purpose in Presto SQL. Do you know any way to efficiently aggregate a group and return its median?

user_10676716 · Answer

approx_percentile() should be a reasonable approach. Assuming a table like mytable(id, val), that you want to aggregate by id:

select id, approx_percentile(val, 0.5) median_val
from mytable
group by id