Remove duplicate rows from a table

deduplicate.sql

with
  dup_id as (select id, count(*) from school group by id having count(*) > 1),
  del_dup as (delete from only school using dup_id where school.id = dup_id.id returning school.*)
insert into school select distinct on (id) del_dup.* from del_dup order by del_dup.id returning *;