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Hadoop Beginner's Guide

You're reading from   Hadoop Beginner's Guide Get your mountain of data under control with Hadoop. This guide requires no prior knowledge of the software or cloud services ‚Äì just a willingness to learn the basics from this practical step-by-step tutorial.

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Product type Paperback
Published in Feb 2013
Publisher Packt
ISBN-13 9781849517300
Length 398 pages
Edition 1st Edition
Tools
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Toc

Table of Contents (19) Chapters Close

Hadoop Beginner's Guide
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
1. What It's All About FREE CHAPTER 2. Getting Hadoop Up and Running 3. Understanding MapReduce 4. Developing MapReduce Programs 5. Advanced MapReduce Techniques 6. When Things Break 7. Keeping Things Running 8. A Relational View on Data with Hive 9. Working with Relational Databases 10. Data Collection with Flume 11. Where to Go Next Pop Quiz Answers Index

Time for action – creating a table from an existing file


So far we have loaded data into Hive directly from files over which Hive effectively takes control. It is also possible, however, to create tables that model data held in files external to Hive. This can be useful when we want the ability to perform Hive processing over data written and managed by external applications or otherwise required to be held in directories outside the Hive warehouse directory. Such files are not moved into the Hive warehouse directory or deleted when the table is dropped.

  1. Save the following to a file called states.hql:

    CREATE EXTERNAL TABLE states(abbreviation string, full_name string)
    ROW FORMAT DELIMITED
    FIELDS TERMINATED BY '\t'
    LOCATION '/tmp/states' ;
  2. Copy the data file onto HDFS and confirm its presence afterwards:

    $ hadoop fs -put states.txt /tmp/states/states.txt
    $ hadoop fs -ls /tmp/states
    

    You will receive the following response:

    Found 1 items
    -rw-r--r--   3 hadoop supergroup        654 2012-03-03 16...
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