title: Limit ammount of rows deleted in table without PK
body: <p>I'm working on a system where, for some reason, someone created a "categories" table without PK'ing the category's ID. I just found out that now the table has a duplicate of all the rows and is causing issues with some of my queries. </p>
  
  <p>My question is: Is there a way to delete duplicate rows, leaving the 'originals' in the table, without relying on indexes?</p>
  
  <p>Here's the <code>SELECT * FROM categories</code>:</p>
  
  <pre><code>+-----------+-------------+
  | categoria | descripcion |
  +-----------+-------------+
  |         1 | Int.Cons.   |
  |         2 | Delegado    |
  |         3 | Personal    |
  |         4 | Comun       |
  |         5 | Proveedor   |
  |         6 | Menor/Inc   |
  |        11 | N/Categoria |
  |         1 | Int.Cons.   |
  |         2 | Delegado    |
  |         3 | Personal    |
  |         4 | Comun       |
  |         5 | Proveedor   |
  |         6 | Menor/Inc   |
  |        11 | N/Categoria |
  +-----------+-------------+
  </code></pre>
  
  <p>There's no index defined on the table.</p>