title: hive left join not working
body: <p>my user table contains following data as columns</p>
  
  <pre><code>region,cust no,mobileno,null,host,null,usage,null,usageduration
  AP      404070620021081 Prepaid 919848052151    NULL    Facebook        NULL    2.9384765625    NULL    1.726
  AP      404070620021081 Prepaid 919848052151    NULL    HTTP    NULL    1.0146484375    NULL    0.232
  AP      404070620021081 Prepaid 919848052151    NULL    Bing    NULL    8.8642578125    NULL    0.746
  AP      404070620021081 Prepaid 919848052151    NULL    Crashlytics     NULL    19.4599609375   NULL    48.765
  AP      404070620021081 Prepaid 919848052151    NULL    DNS     NULL    17.4296875      NULL    584.596
  AP      404070620021081 Prepaid 919848052151    NULL    Doubleclick     NULL    6.908203125     NULL    1.362
  AP      404070620021081 Prepaid 919848052151    NULL    Dropbox NULL    37.0380859375   NULL    42.174
  AP      404070620021081 Prepaid 919848052151    NULL    Facebook        NULL    21.1533203125   NULL    29.689
  AP      404070620021081 Prepaid 919848052151    NULL    Google  NULL    49.0732421875   NULL    28.456
  AP      404070620021081 Prepaid 919848052151    NULL    Google APIs     NULL    213.8642578125  NULL    49.866
  AP      404070620021081 Prepaid 919848052151    NULL    Google Ads      NULL    5.7314453125    NULL    0.932
  AP      404070620021081 Prepaid 919848052151    NULL    Google Calendar NULL    0.201171875     NULL    0.06
  AP      404070620021081 Prepaid 919848052151    NULL    Google Cloud Messaging  NULL    8.5419921875    NULL    143.50799999999998
  AP      404070620021081 Prepaid 919848052151    NULL    Google Play     NULL    228.7880859375  NULL    88.77600000000001
  AP      404070620021081 Prepaid 919848052151    NULL    HTTP    NULL    0.29296875      NULL    1.16
  AP      404070620021081 Prepaid 919848052151    NULL    NTP     NULL    0.1484375       NULL    0.122
  AP      404070620021081 Prepaid 919848052151    NULL    SSL     NULL    96.095703125    NULL    452.88
  AP      404070620021081 Prepaid 919848052151    NULL    Skype   NULL    93.6953125      NULL    67.649
  AP      404070620021081 Prepaid 919848052151    NULL    TCP     NULL    93.591796875    NULL    117.32900000000001
  AP      404070620021081 Prepaid 919848052151    NULL    WhatsApp        NULL    165780.6171875  NULL    1097.055
  AP      404070620021081 Prepaid 919848052151    NULL    XMPP    NULL    62.4453125      NULL    350.03700000000003
  
  
  my top20 table contains host,rank
  SSL                     1
  TCP                     2
  DNS                     3
  HTTP                    4
  Facebook                5
  Google Play             6
  Google Cloud Messaging  7
  YouTube                 8
  UDP                     9
  XMPP                    10
  Skype                   11
  WhatsApp                12
  Bittorrent              13
  Google                  14
  STUN                    15
  Google APIs             16
  Doubleclick             17
  Apple                   18
  MDNS                    19
  Google Ads              20
  </code></pre>
  
  <p>i need usage,duration for each customer for these top20 sites.if customer didnt used then it should show 0 but 20 rows required for each customer. i done left join but gettin 420 rows with all combination.which is wrong.please suggest to get 20 rows for each customer</p>