title: GROUP BY with only first row of sequence of one column?
body: <p>at first here is the alpha version of what I want: <a href="http://sqlfiddle.com/#!2/45c89/2" rel="nofollow">http://sqlfiddle.com/#!2/45c89/2</a></p>
  
  <p>However I don't want to count all representative_id, but only this rows with the lowest id, eg:</p>
  
  <pre><code>(`id`, `economy_id`, `representative_id`)
  (1, 1, 5), &lt;-this one, lowest id through the same economy_id=1
  (2, 1, 6),
  (3, 1, 7),
  (4, 1, 8),
  (5, 1, 3),
  (6, 1, 4),
  (7, 1, 1),
  (8, 1, 2),
  (9, 1, 102),
  (10, 2, 7), &lt;-this one, lowest id through the same economy_id=2
  (11, 2, 8),
  (12, 2, 102),
  (13, 2, 1),
  (14, 2, 2),
  (15, 2, 3),
  (16, 2, 4),
  (17, 3, 3), &lt;-this one, lowest id through the same economy_id=3
  (18, 3, 4),
  (19, 3, 1),
  (20, 3, 2),
  (21, 3, 102),
  (22, 4, 1), &lt;-this one, lowest id through the same economy_id=4
  (23, 4, 2),
  (24, 4, 102),
  (25, 5, 1),  &lt;-this one, lowest id through the same economy_id=5
  (26, 5, 2),
  (27, 5, 102),
  (28, 5, 7),
  (29, 6, 1),  &lt;-this one, lowest id through the same economy_id=6
  </code></pre>
  
  <p>The output should be:</p>
  
  <p>representative_id, count()</p>
  
  <p>According to above example:</p>
  
  <pre><code>5, 1
  7, 1
  3, 1
  1, 3
  </code></pre>
  
  <p>Is it possible only in SQL?</p>