Migrating from a structured schema to a schema-less form is not very hard. In many cases you could simply export the data from Rdbms tables and move them into Nosql collections. However, things get complicated when the NoSQL database is a column-family, sorted ordered, or a key/value store. Changes in paradigm often lead to redesign efforts.

The greater impedance mismatch is around ad-hoc querying and secondary indexes, which are often difficult to support in a NoSQL environment. NoSQL looks at the data store from a query perspective and not from a generic storage viewpoint.

To facilitate data importation from RDBMS to Hadoop for NoSQL-style manipulations, Cloudera has created an open-source product called Sqoop. Sqoop is a command-line tool with the following capabilities:

» Imports individual RDBMS tables or entire databases to fi les in HDFS
» Generates Java classes to allow you to interact with your imported data
» Provides the ability to import from SQL databases straight into your Hive data warehouse

You can learn more about Sqoop at https://github.com/cloudera/sqoop.

Source of Information : NoSQL