title: MySQL group by, but show all and order by date
body: <p>I have the following mysql table </p>
  
  <pre><code>ID (int)        parent_id (int)        title (str)     date (int - unix timestamp)
  ------------------------------------------------------------------------------------
  252                 2                  Title 1         1378872876  (01. sept)
  262                 2                  Title 2         1378870827  (02. sept)
  273                 3                  Title 3         1378870800  (04. sept)
  296                 3                  Title 4         1378869614  (05. sept)
  301                 2                  Title 5         1378869384  (02. sept)
  324                 4                  Title 6         1378868522  (02. sept)
  339                 3                  Title 7         1378865096  (03. sept)
  355                 3                  Title 8         1378864830  (02. sept)
  365                 4                  Title 9         1378863323  (04. sept)
  366                 4                  Title 10        1378863240  (02. sept)
  376                 2                  Title 11        1378859731  (01. sept)
  381                 5                  Title 12        1378858380  (03. sept)
  388                 3                  Title 13        1378858080  (02. sept)
  392                 4                  Title 14        1378857600  (04. sept)
  </code></pre>
  
  <p>What i want to do is to select all rows ordered by the unix timestamp (only day), but also group by parent_id. So, the SQL query should return the following:</p>
  
  <pre><code>ID (int)        parent_id (int)        title (str)     date (int - unix timestamp)
  ------------------------------------------------------------------------------------
  296                 3                  Title 4         1378869614  (05. sept)
  273                 3                  Title 3         1378870800  (04. sept)
  339                 3                  Title 7         1378865096  (03. sept)
  388                 3                  Title 13        1378858080  (02. sept)
  355                 3                  Title 8         1378864830  (02. sept)
  392                 4                  Title 14        1378857600  (04. sept)
  365                 4                  Title 9         1378863323  (04. sept)
  366                 4                  Title 10        1378863240  (02. sept)
  324                 4                  Title 6         1378868522  (02. sept)
  381                 5                  Title 12        1378858380  (03. sept)
  262                 2                  Title 2         1378870827  (02. sept)
  301                 2                  Title 5         1378869384  (02. sept)
  252                 2                  Title 1         1378872876  (01. sept)
  376                 2                  Title 11        1378859731  (01. sept)
  </code></pre>
  
  <p>I have tried the following but it isn't really what i want:</p>
  
  <pre><code> SELECT 
           f.*, 
           FROM_UNIXTIME(f.post_date , '%d' ) AS day, 
           FROM_UNIXTIME(f.post_date , '%H' ) AS hour 
      FROM feeds f 
      WHERE f.parent_id IN (200,194,176,182,190,181,189,196,191) 
      GROUP BY f.parent_id 
      ORDER BY f.post_date DESC  
      LIMIT 0,100
  </code></pre>
  
  <p>Can this be done only with mysql or do I have to build multiple queries?</p>