postgreSQL ranking query with the given user_id - php

Question

I am trying to get rank of a user by their two dimension params: donation sum and total donor count.
My rank formula is: rank of [rank of donation_sum + rank of donor_count / 2]
Sample table:
donation_id | user_id | donor_id | donation_sum
-----------------------------------------------
1 | 1 | 1 | 10
2 | 1 | 2 | 5
3 | 2 | 3 | 10
4 | 3 | 1 | 50
...
As you see, some donors make donation to different users, so I used sum(donation_sum) and count(distinct(donation_id)) to get exact rankings
I am able to get list of ranking separately by donation sum and total donor count with 2 sql but my need is to get a user rank with that formula above by given user_id in postgreSQL v. 9.4
Do you have any solution for it? so I will use that sql query in a Yii2 PHP framework
Thanks
Edit:
We added donation_date to the tbl_donation and modified actual query as below:
is it true usage of where donation_date?
with list as (
select
s.runner_id, sum, count, rank_sum, rank_count,
(rank_sum+ rank_count)::float/ 2 as rank_avg,
row_number() over (order by rank_sum) as rank
from (
select *, rank() over (order by sum desc) rank_sum
from (
select runner_id, sum(donation_sum)
from tbl_donation
where donation_date >= '2015-01-01'
group by 1
) s
) s
join (
select *, rank() over (order by count desc) rank_count
from (
select runner_id, count(distinct(donator_id))
from tbl_donation
where donation_date >= '2015-01-01'
group by 1
) c
) c
using (runner_id)
)
select rank
from list
where runner_id = 251;

Answer 1

Make two rankings in separate subqueries:
select
s.user_id, sum, count, rank_sum, rank_count,
(rank_sum+ rank_count)::float/ 2 as rank_avg,
row_number() over (order by rank_sum) as rank
from (
select *, rank() over (order by sum desc) rank_sum
from (
select user_id, sum(donation_sum)
from donations
group by 1
) s
) s
join (
select *, rank() over (order by count desc) rank_count
from (
select user_id, count(distinct(donation_id))
from donations
group by 1
) c
) c
using (user_id);
user_id | sum | count | rank_sum | rank_count | rank_avg | rank
---------+-----+-------+----------+------------+----------+------
3 | 100 | 1 | 1 | 2 | 1.5 | 1
1 | 30 | 2 | 2 | 1 | 1.5 | 2
2 | 20 | 1 | 3 | 2 | 2.5 | 3
(3 rows)
If you want to select rank for a single user_id use with query, e.g.:
with list as (
-- place here the above query
)
select rank
from list
where user_id = 2;