Oracle aggregate function to return a random value for a group?

Question

The standard SQL aggregate function max() will return the highest value in a group; min() will return the lowest.

Is there an aggregate function in Oracle to return a random value from a group? Or some technique to achieve this?

E.g., given the table foo:

group_id value
1        1
1        5
1        9
2        2
2        4
2        8

The SQL query

select group_id, max(value), min(value), some_aggregate_random_func(value)
from foo
group by group_id;

might produce:

group_id  max(value), min(value), some_aggregate_random_func(value)
1        9            1           1
2        8            2           4

with, obviously, the last column being any random value in that group.

Answer 1

You can try something like the following

select deptno,max(sal),min(sal),max(rand_sal) 
from(
select deptno,sal,first_value(sal) 
     over(partition by deptno order by dbms_random.value) rand_sal
from emp)
group by deptno
/

The idea is to sort the values within group in random order and pick the first.I can think of other ways but none so efficient.