Question

I have the following problem (simplified):

I have a table that contains animals, e.g:

ID       Type      Birthday
1        Dog       1.1.2011  
2        Cat       2.1.2009
3        Horse     5.1.2009
4        Cat       10.6.1999
5        Horse     9.3.2006

I know that all the animals belong to one “family”. From each family I now want to see all the offspring, but I do not want to see the entry for the “founder of the family”.

So for the simple sample above I just want to see this:

ID       Type      Birthday
2        Cat       2.1.2009
3        Horse     5.1.2009

So far I haven’t been able to find a way of grouping the entries and then removing the first entry from each group. I was only able to find how to remove specific lines.

Is it even possible to solve this problem?

Thank you very much for your help. It is much appreciated.

Answer 1

A simple SQL(not necessary efficient can be:)

select
  id, type, birthday
from animals
  left join
  (select type, min(birthday) min_birthday
  from animals
  group by type) a 
     on a.type=animals.type and a.min_birthday = animals.birthday
where a.type is null;

For best efficiency you can use an analytical function:

select id, type, birthday
from(
    select
      id, 
      type, 
      birthday, 
      row_number() over (partition by type order by birthday) as rnk
    from animals
) a
where rnk >=2

For more examples with analytical functions, you can read this article