title: SQL query to join rows with same values
body: <p>I've come across a problem that I don't really know how to solve.
  I have a table which looks somewhat like this:</p>
  
  <pre><code>ID   Name     Price     Quantity
  1    BookA      5         10
  2    BookB     10         15
  3    BookA     15         15
  4    BookA      5         25
  </code></pre>
  
  <p>How could I join rows which have same Name, same Price and sum Quantity? So it would look like this:</p>
  
  <pre><code>ID   Name     Price     Quantity
  1    BookA      5         35
  2    BookB     10         15
  3    BookA     15         15
  </code></pre>
  
  <p>Thank you in advance!</p>