What is Sqoop
Sqoop is a command-line interface application for transferring data between relational databases and Hadoop.
It supports incremental loads of a single table or a free form SQL query as well as saved jobs which can be run multiple times to import updates made to a database since the last import.Using Sqoop, Data can be moved into HDFS/hive/hbase from MySQL/ PostgreSQL/Oracle/SQL Server/DB2 and vise versa.
Step 1: Sqoop send the request to Relational DB to send the return the metadata informationabout the table(Metadata here is the data about the table in relational DB).
Step 2: From the received information it will generate the java classes (Reason why you shouldhave Java configured before get it working-Sqoop internally uses JDBC API to generate data).
Step 3: Now Sqoop (As its written in java ?tries to package the compiled classes to beable togenerate table structure) , post compiling creates jar file(Java packaging standard).