Understanding Joins in MapReduce | Comprehensive MapReduce Tutorial | Edureka

( Comprehensive MapReduce Certification Training - https://www.edureka.co/comprehensive-mapreduce-self-paced ) Watch Sample Class recording: http://www.edureka.co/comprehensive-mapreduce?utm_source=youtube&utm_medium=referral&utm_campaign=joins-comprehensive Join is a clause that combines the records of two tables (or Data-Sets). Whenever, we apply join operation, the job will be assigned to a Map Reduce task which consists of two stages- a ‘Map stage’ and a ‘Reduce stage’. A mapper’s job during Map Stage is to “read” the data from join tables and to “return” the ‘join key’ and ‘join value’ pair into an intermediate file. Further, in the shuffle stage, this intermediate file is then sorted and merged. The reducer’s job during reduce stage is to take this sorted result as input and complete the task of join. Edureka is a New Age e-learning platform that provides Instructor-Led Live, Online classes for learners who would prefer a hassle free and self paced learning environment, accessible from any part of the world. The topics related to Mapreduce have extensively been covered in our course 'Comprehensive MapReduce' For more information, please write back to us at [email protected] Call us at US: 1800 275 9730 (toll free) or India: +91-8880862004