title: MySql Single Table, Select last 7 days and include empty rows
body: <p>I have searched similar problems here on stackoverflow but I could not understand how to make this work, what I'm trying to do...</p>
  
  <p>So, I want to get last 7 days transactions from database and get total sales amount and also include empty rows if there is no data for some day.</p>
  
  <p>What I have so far:
  <a href="http://sqlfiddle.com/#!2/f4eda/6" rel="nofollow">http://sqlfiddle.com/#!2/f4eda/6</a></p>
  
  <p>This outputs: </p>
  
  <pre><code>| PURCHASE_DATE | AMOUNT |
  |---------------|--------|
  |    2014-04-25 |     19 |
  |    2014-04-24 |     38 |
  |    2014-04-22 |     19 |
  |    2014-04-19 |     19 |
  </code></pre>
  
  <p>What I want:  </p>
  
  <pre><code>| PURCHASE_DATE | AMOUNT |
  |---------------|--------|
  |    2014-04-25 |     19 |
  |    2014-04-24 |     38 |
  |    2014-04-23 |      0 |
  |    2014-04-22 |     19 |
  |    2014-04-21 |      0 |
  |    2014-04-20 |      0 |
  |    2014-04-19 |     19 |
  </code></pre>
  
  <p>Any help appreciated :)</p>