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Sqoop Interview Questions and Answers

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Sqoop Interview Questions and Answers
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What is sqoop and What does sqoop stand for?

Sqoop stands for SQL to Hadoop and Hadoop to SQL. The Apache Sqoop is a component within the Hadoop ecosystem. It helps in the movement of data between the different relational database servers in the Hadoop file structure.  It can pull data from other relational databases such as Oracle to the Hadoop file system.

What is sqoop used for?

The primary task of Sqoop is to transfer bulk information between relational database servers. Sqoop helps the developers to handle these huge bulks of data which in turn helps them to gather relevant insights from the data. It eases up the process and allows better export and import of information.

What is the default database of Sqoop?

The default database of Sqoop is MySql.

How to check sqoop version?

The Sqoop version can be checked using the following command in the command line:

sqoop version

How to set a number of mappers in Apache sqoop?

Sqoop controls the number of mappers that are currently accessing the RDBMS to avoid the DOS attacks on the entire system. This number of mappers can be set using the following command:

clause-m or numb-mappers.

For example,  numb-mappers 10.

What is sqoop direct mode?

Using the direct mode in Sqoop, we can mention that Sqoop must use the direct import channel. This argument is used with the import command and can be used only with PostGreSQL and MySql.

How to delete sqoop job?

A job can be deleted in Sqoop by the following syntax:

--delete <job id>

This is used to delete save d jobs.

What is sqoop eval tool?

The primary task of the Sqoop Eval is to let the users execute simple database queries. Both DDL and DML statements can be executed easily using Sqoop Eval.     

Why sqoop is used in Hadoop?

Sqoop is used to import datasets into the HDFS. It can also be used for export datastores from Hadoop to external databases. Sqoop is easier to use while transferring data for the developers, as it automates the process. It makes use of the MapReduce framework to transfer data, that provides fault tolerance. It is easy to use Sqoop as it has a command based interface.

What is boundary query in sqoop?

The valid query required to obtain the minimum and maximum values for the column split using split by command can be mentioned using the boundary query parameter.

How to import multiple tables in sqoop?

The import all tables tool can be used to import multiple tables in Sqoop. The following syntax has to be used:

$ sqoop import-all-tables (generic-args) (import-args)

However, to use the tool successfully, the following conditions have to be met:

  • The tables should have a single column primary key.
  • All the columns of each table must be imported.
  • Using conditions having a WHERE clause and non-default splitting columns must be avoided.

How to change sqoop date format?

The date format is Sqoop can be altered by the SET DATEFORMAT 'ymd' just after starting the connection.

What is the difference between Sqoop and Flume?

The difference between Sqoop and Flume is depicted below:

Sqoop

Flume

It is used for importing and exporting datastores from relational databases.

It is used for pulling logs and crash reports into the Hadoop file system.

It does not have event-driven loading.

It has event-driven loading.

It has an architecture based on connectors.

It has an architecture based on agents, where the agent code is used to pull the data.

Used to move data faster to produce analytic results.

It is used when the analysis of patterns and root causes is necessary for corporations.

What happens when Sqoop fails in between the large data transfer job?

During data transfer between two databases, if the job fails, some portion of the data might get saved in the database. This can be solved by using the staging table option.

What is the use of split by in sqoop?

The split by command is used to mention the column that will be used to split the data that is being imported while data transfer. Based on certain column values, Sqoop uses split by to split the data.

How to use split by in sqoop?     

The split by command can be used in Sqoop using the following syntax:

--split-by student.id 

This command will split the data while importing based on the student.id values.

What is accumulo in sqoop?

The Apache Acccumulo is a key value store that is developed over the Hadoop File system. The handling of larger sets of data is easier with Accumulo. The data in Accumulo is stored in the Haddop File system. In Sqoop, there is a functionality that allows users to directly import a table from the Accumulo data store.

How to grant access on password file in Sqoop?

The password file option can be used to access the protected file. The file can be present in the HDFS directory or it can be kept in the system where the command is being executed. The following code will be needed:

$echo -n "password" > /etc/sqoop/conf/passwords/mysql-password.txt

$chmod 400 /etc/sqoop/conf/passwords/mysql-password.txt

$sqoop import --connect jdbc:netezza://localhost/MYDB

--username testuser 

--table ORDERS 

--password-file /etc/sqoop/conf/passwords/mysql-password.txt

How the increment works in sqoop, do we have to manually provide the last modified value every time?

The incremental imports in Sqoop is of two types, lastmodified and append. The incremental import allows the users to obtain the rows that are recently imported, rather than the older rows.

When an import ends, the last value that can be used for another incremental import is provided in the console.  This value must be provided in subsequent incremental imports to ensure that updated information is imported.

How much memory does a sqoop client require to initialize the job?

A Sqoop client may require a minimum of 1Gb of memory to initialize a job.

Define free form import in sqoop.

Free-form query import allows the users to mention the query they want to use while importing data. The query parameter will be used.

What is boundary query in sqoop?  

The valid query required to obtain the minimum and maximum values for the column split using split by command can be mentioned using the boundary query parameter.

How to pass the schema name in the sqoop?

The schema name can be provided by using the following syntax:

$ sqoop import ... --table custom_table -- --schema custom_schema

What is the syntax to see db in sqoop?

The databases can be viewed by using the following command:

$sqoop  list-databases 

Why to use $conditions in sqoop?

The $conditions are used in Sqoop to support parallelism while splitting your query into parts. Inside the WHERE clause of the query, the $CONDITIONS placeholder is placed. It is used to provide a WHERE clause that is explicit.


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