How to get non-unique values?

Question

SQL

How to get non-unique records of the objs table by the id field, so that they can be deleted later, for example?
I try select id from objs group by id having count(*) >1, but it does not display anything, although there are such entries.

Answer 1

having count(*) > 1
by the way, removing not all "duplicates", but only N-1 will not be such a trivial task -)