301.4.7-Joins

Joins

• Two Tables

Retail_invoice = LOAD '/Retail_invoice_hdfs' USING PigStorage('\t') as (uniq_idi:chararray, InvoiceNo:chararray, StockCode:chararray, Description:chararray,Quantity:INT);
DESCRIBE Retail_invoice;

Retail_Customer = LOAD '/Retail_Customer_hdfs' USING PigStorage('\t') as (uniq_idc:chararray, InvoiceDate:chararray, UnitPrice:INT, CustomerID:chararray,Country:chararray);
DESCRIBE Retail_Customer;

Left Outer Join

Left_join = JOIN Retail_invoice BY uniq_idi LEFT OUTER, Retail_Customer BY uniq_idc;
DESCRIBE Left_join;

DUMP Left_join;

Right Outer Join

Right_join = JOIN Retail_invoice BY uniq_idi RIGHT OUTER, Retail_Customer BY uniq_idc;
DESCRIBE Right_join;

DUMP Right_join;

Full Outer Join

Full_join = JOIN Retail_invoice BY uniq_idi FULL, Retail_Customer BY uniq_idc;
DESCRIBE Full_join;

DUMP Full_join;

Inner Join

Inner_join = JOIN Retail_invoice BY uniq_idi , Retail_Customer BY uniq_idc;
DESCRIBE Inner_join;

    DUMP Inner_join;

Storing the Results on Pig

• Similar to exporting the analysis resultant table out of Pig
• After the final analysis in pig we may have the final Relation in pig.
• Store helps us to export the relation(resultant data) out of pig
• STORE is the opposite of LOAD. We used LOAD for loading data from HDFS to a Relation
• STORE is used for loading data from Relation to HDFS.

hadoop fs -ls /

STORE Inner_join INTO '/pig_Inner_join/' USING PigStorage (',');

hadoop fs -ls /

hadoop fs -rmr /pig_datsets

Check on http://localhost:50070/explorer.html#/

History

• History helps us to see all the command we ran in order

history