SQL Oracle: How to show only one row when the columns diverge

Question

I have an employees table in which most of the results show me only one employee per row.

However, I have to bring the amount of employees by area where 3 employees out of the 3432 have worked on a different area before.

Therefore, the results show me duplicated rows for these 3 employees. It's something like this:

Notice that on Brian's situation he's been admitted on a different area before.

How can I show Brian only once? Nonetheless, how can I show only the most recent area where he's worked on?

Answer 1

You can use ROW_NUMBER() to identify new and old rows per each employee, ordered by admission date.

Then filtering out old rows is easy. For example:

select *
from (
  select t.*,
    row_number() over(partition by employee order by admission desc) as rn
  from t
) x
where rn = 1 -- keeps the latest row only, per employee