title: Putting two rows together on the same row in Oracle
body: <p>Let's take as example this table, which associate a product to the number 
  of stars he received from customer's feedbacks (it happens to be ordered by number of stars):</p>
  
  <pre><code>| ProductID |  Stars  | 
  |-----------|---------|
  |    23     |    10   |
  |    12     |    10   |
  |    17     |     9   |
  |     5     |     8   |
  |    20     |     8   |
  |    18     |     7   |  
  </code></pre>
  
  <p>How would I select (showing them on the same row) the IDs of the products
  in pairs?</p>
  
  <p>Like this:</p>
  
  <pre><code>|  Product1 |   Product2  | 
  |-----------|-------------|
  |    23     |      12     |
  |    17     |       5     |
  |    20     |      18     |  
  </code></pre>
  
  <p>Or like this:</p>
  
  <pre><code>|     Products     | 
  |------------------|
  |    23     12     |
  |    17      5     |
  |    20     18     |
  </code></pre>