title: select all duplicates from a table in postgres
body: <p>Is there a simple way to select all duplicates from a Postgres table? No need for joins or anything fancy. Everything I find on stack is about joins and duplicates involving multiple fields on a table.</p>
  
  <p>I just need to <code>select * from table where table contains duplicate entries</code></p>
  
  <p>Any ideas?</p>
  
  <h2>Table definition from Postgres:</h2>
  
  <pre><code>scotchbox=# \d+ eve_online_market_groups
  
                                                             Table "public.eve_online_market_groups"
     Column   |              Type              |                               Modifiers                               | Storage  | Stats target | Description 
  ------------+--------------------------------+-----------------------------------------------------------------------+----------+--------------+-------------
   id         | integer                        | not null default nextval('eve_online_market_groups_id_seq'::regclass) | plain    |              | 
   name       | character varying(255)         | not null                                                              | extended |              | 
   item_id    | integer                        | not null                                                              | plain    |              | 
   slug       | character varying(255)         | not null                                                              | extended |              | 
   created_at | timestamp(0) without time zone |                                                                       | plain    |              | 
   updated_at | timestamp(0) without time zone |                                                                       | plain    |              | 
  Indexes:
      "eve_online_market_groups_pkey" PRIMARY KEY, btree (id)
  Has OIDs: no
  </code></pre>