I want to return all the data, from max count query with hospital that has most number of patients. What I seem to be getting when I try to nest queries is display of all rows of hospital data. I've tried to look at similar questions in stack overflow and other sites it seems to be a simple query to do but i am not getting it.
select max(highest_hospital) as max_hospital
from (select count(hospital) as highest_hospital
from doctor
group by hospital)
highest_hospital
-------------
3
Doc ID Doctor Patient Hospital Medicine Cost
------ ------- ------ --------- ------ --------
1 Jim Bob Patient1 Town 1 Medicine 1 4000
2 Janice Smith Patient2 Town 2 Medicine 3 3000
3 Harold Brown Patient3 Town 2 Medicine 5 2000
4 Larry Owens Patient4 Town 2 Medicine 6 3000
5 Sally Brown Patient5 Town 3 Medicine 7 4000
6 Bob Jim Patient6 Town 4 Medicine 8 6000
Outcome should be return of 3 rows
Doc ID Doctor Patient Hospital Medicine Cost
------ ------- ------ --------- ------ --------
2 Janice Smith Patient2 Town 2 Medicine 3 3000
3 Harold Brown Patient3 Town 2 Medicine 5 2000
4 Larry Owens Patient4 Town 2 Medicine 6 3000
You can use window functions:
select d.*
from (select d.*, max(hospital_count) over () as max_hospital_count
from (select d.*, count(*) over (partition by hospital) as hospital_count
from doctor d
) d
) d
where hospital_count = max_hospital_count;
Edit:
Using GROUP BY is a pain. If you are only looking for a single hospital (even when there are ties), then in Oracle 12C you can do:
select d.*
from doctor d
where d.hospital = (select d2.hospital
from doctor d2
group by d2.hospital
order by count(*) desc
fetch first 1 row only
);
You can do this in earlier versions of Oracle using an additional subquery.