The ORDER BY operator is used to display the contents of a relation in a sorted order based on one or more fields.
Syntax
Given below is the syntax of the ORDER BY operator.
grunt> Relation_name2 = ORDER Relatin_name1 BY (ASC|DESC);
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,21,9848022337,Hyderabad 002,siddarth,Battacharya,22,9848022338,Kolkata 003,Rajesh,Khanna,22,9848022339,Delhi 004,Preethi,Agarwal,21,9848022330,Pune 005,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar 006,Archana,Mishra,23,9848022335,Chennai 007,Komal,Nayak,24,9848022334,trivendram 008,Bharathi,Nambiayar,24,9848022333,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,age:int, phone:chararray, city:chararray);
Let us now sort the relation in a descending order based on the age of the student and store it into another relation named order_by_data using the ORDER BY operator as shown below.
grunt> order_by_data = ORDER student_details BY age DESC;
Verification
Verify the relation order_by_data using the DUMP operator as shown below.
grunt> Dump order_by_data;
Output
It will produce the following output, displaying the contents of the relation order_by_data.
(8,Bharathi,Nambiayar,24,9848022333,Chennai) (7,Komal,Nayak,24,9848022334,trivendram) (6,Archana,Mishra,23,9848022335,Chennai) (5,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar) (3,Rajesh,Khanna,22,9848022339,Delhi) (2,siddarth,Battacharya,22,9848022338,Kolkata) (4,Preethi,Agarwal,21,9848022330,Pune) (1,Rajiv,Reddy,21,9848022337,Hyderabad)