Apr 29 2014 12:26 PM
There can be many use cases where you would want to export data from HDFS back into RDBMS.
One thing to remember is Hadoop is used for performing offline analysis of data. So once you perform that analysis using MapReduce or Pig or Hive - you might want to store the results of that analysis into RDBMS so its accessible in real time over the web.
For example many companies analyse their weblogs using either MapReduce,Pig or Hive and export the summary of the weblog data into an RDBMS.
Hope this helps