Group by returning more than one column in a single query

Question

Hello,
Sorry to ask such a simple question I guess, but here is my problem.
I'm building a query to get say the smallest user_id from employees in the company by department.
The query goes like :
select emp..department,
min(emp.user_id)
from employee emp
group by emp.department
This gives me the smallest user id by department, which is what I want. But how can I also get the name of that person ?
I know that the "min" condition singles out a unique record (there are no two persons with the same user_id in the department).
But how can I also get the name without turning the above query in a subquery that I would link to the employee table yet again ?
I know the following works but I don't think it's the best option:
select v1.department,
v1.user_id,
emp1.name
from employee emp1,
( select emp..department,
min(emp.user_id)
from employee emp
group by emp.department) v1
where emp1.user_id = v1.user_id
This is just an example of data. It is the principle that I don't quite get.
Any advice would be very much appreciated.
Cyril

Answer 1

Hi, Cyril,
To find the name of the person who has the lowest user_id
SELECT    department
,         MIN (user_id)   AS lowest_user_id
,         MIN (name) KEEP (DENSE_RANK FIRST ORDER BY user_id)  AS person_with_lowest_user_id
FROM      emp
GROUP BY  department;"MIN (name)" above means that if there is a tie for the lowest user_id, then the contender with the first name will be chosen.
If you want to display several columns from the row with the lowest user_id, you have to have a separate "KEEP (DENSE_RANK ...)" expression for each column. In that case, you may find it easier to use the analytic RANK or ROW_NUMBER in a sub-query, like this:
WITH  sub_query  AS
     SELECT  department
     ,     user_id
     ,     name
     ,     col2, col3, col4, col5
     ,     RANK () OVER ( PARTITION BY  department
                           ORDER BY          user_id
                    )  AS r_num
     FROM     emp
SELECT     *     -- or list all columns EXCEPT r_num
FROM     sub_query
WHERE     r_num = 1;