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The DISTINCT operator is used to remove redundant (duplicate) tuples from a relation.
Syntax
Given below is the syntax of the DISTINCT operator.
grunt> Relation_name2 = DISTINCT Relatin_name1;
Example
Assume that we have a file named student_details.txt in the HDFS directory /pig_data/ as shown below.
student_details.txt
001,Rajiv,Reddy,9848022337,Hyderabad 002,siddarth,Battacharya,9848022338,Kolkata 002,siddarth,Battacharya,9848022338,Kolkata 003,Rajesh,Khanna,9848022339,Delhi 003,Rajesh,Khanna,9848022339,Delhi 004,Preethi,Agarwal,9848022330,Pune 005,Trupthi,Mohanthy,9848022336,Bhuwaneshwar 006,Archana,Mishra,9848022335,Chennai 006,Archana,Mishra,9848022335,Chennai
And we have loaded this file into Pig with the relation name student_details as shown below.
grunt> student_details = LOAD ''hdfs://localhost:9000/pig_data/student_details.txt'' USING PigStorage('','') as (id:int, firstname:chararray, lastname:chararray, phone:chararray, city:chararray);
Let us now remove the redundant (duplicate) tuples from the relation named student_details using the DISTINCT operator, and store it as another relation named distinct_data as shown below.
grunt> distinct_data = DISTINCT student_details;
Verification
Verify the relation distinct_data using the DUMP operator as shown below.
grunt> Dump distinct_data;
Output
It will produce the following output, displaying the contents of the relation distinct_data as follows.
(1,Rajiv,Reddy,9848022337,Hyderabad) (2,siddarth,Battacharya,9848022338,Kolkata) (3,Rajesh,Khanna,9848022339,Delhi) (4,Preethi,Agarwal,9848022330,Pune) (5,Trupthi,Mohanthy,9848022336,Bhuwaneshwar) (6,Archana,Mishra,9848022335,Chennai)
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