title: basic sql : selecting AVG() values from the same column multiple times in one query, when each wanted AVG() value uses different WHERE clause
body: <p>I want to get three different average values from one column (value_to_count) inside one table where all of those average values has a different WHERE clause (according to time).</p>
  <h3>Example Data:</h3>
  <pre><code>###services#### Table
  service_id       value_to_count                time
  -----------      -----------------------       ---------
       604                    2054               04:04:50
       604                    3444               05:00:15
       604                    2122               07:12:50
       604                    2144               09:10:50
       604                    2001               13:12:53
       602                    2011               15:00:12
       602                    2115               17:22:35
       602                    1411               20:22:12
       602                    1611               21:04:52
       602                    2111               23:43:45
  </code></pre>
  <p>I'm using this query at the moment to get the average value on time between 18 and 23:</p>
  <h3>Query</h3>
  <pre><code>SELECT 
  service_id AS service, AVG(value_to_count) AS primetime 
  FROM services 
  WHERE HOUR(time) BETWEEN 18 AND 23 
  GROUP BY service_id
  </code></pre>
  <p>And it gives me this kind of results:</p>
  <pre><code>### Result #### 
  service          primetime
  -----------      --------------      
       604               2154           
       602               2444           
  </code></pre>
  <p>Now I want to get other average values next to the one I already got. This time I just want to get averages by 'HOUR(time) BETWEEN 06 AND 18' and 'HOUR(time) BETWEEN 23 AND 06' aswell.</p>
  <p>This is the form of result I want to get:</p>
  <pre><code>### Wanted Result #### 
  service          primetime          other_time_interval_1   other_time_interval_2
  -----------      --------------     ----------------        ------------------
       604               2154              2352                      1842
       602               2444              4122                      1224
  </code></pre>