title: group by with interval of time in hive gives null output
body: <p>I have a dataset , which looks like following-</p>
  
  <pre><code>Name    Time
  A   00:00:00
  B   00:03:53
  C   00:01:16
  A   00:04:34
  A   00:07:32
  A   00:18:36
  C   00:16:12
  C   00:05:04
  E   00:01:50
  D   00:12:05
  A   00:11:20
  B   00:04:27
  D   00:02:47
  A   00:00:23
  I   00:00:23
  F   00:36:21
  F   00:02:46
  </code></pre>
  
  <p>I am trying to divide the destination ,for each 6 minutes interval since 00.00.00
  So the hive query I came up with-</p>
  
  <pre><code>select name,count(1),FLOOR(UNIX_TIMESTAMP(time)/360) from csvlog GROUP BY name , FLOOR(UNIX_TIMESTAMP(time)/360) limit 10;
  </code></pre>
  
  <p>And the output I am getting -</p>
  
  <pre><code>A   1062    NULL
  B   8   NULL
  C   4   NULL
  D   6   NULL
  E   6   NULL
  F   5   NULL
  G   1   NULL
  H   2   NULL
  I   7   NULL
  </code></pre>
  
  <p>NULL is the value , I didn't expect.
  I am just 1 day old in Hive so I may be doing something wrong.
  I was expecting time as a value .</p>