Featured Post

Step-by-Step Guide to Creating an AWS RDS Database Instance

-
Image
 Amazon Relational Database Service (AWS RDS) makes it easy to set up, operate, and scale a relational database in the cloud. Instead of managing servers, patching OS, and handling backups manually, AWS RDS takes care of the heavy lifting so you can focus on building applications and data pipelines. In this blog, we’ll walk through how to create an AWS RDS instance , key configuration choices, and best practices you should follow in real-world projects. What is AWS RDS? AWS RDS is a managed database service that supports popular relational engines such as: Amazon Aurora (MySQL / PostgreSQL compatible) MySQL PostgreSQL MariaDB Oracle SQL Server With RDS, AWS manages: Database provisioning Automated backups Software patching High availability (Multi-AZ) Monitoring and scaling Prerequisites Before creating an RDS instance, make sure you have: An active AWS account Proper IAM permissions (RDS, EC2, VPC) A basic understanding of: ...
Post a Comment

Spark SQL Query how to write it in Ten steps

-
Spark SQL example
Spark SQL example
The post tells how to write SQL query in Spark and explained in ten steps.This example demonstrates how to use sqlContext.sql to create and load two tables and select rows from the tables into two DataFrames.

The next steps use the DataFrame API to filter the rows for salaries greater than 150,000 from one of the tables and shows the resulting DataFrame. Then the two DataFrames are joined to create a third DataFrame. Finally the new DataFrame is saved to a Hive table.

1. At the command line, copy the Hue sample_07 and sample_08 CSV files to HDFS:
$ hdfs dfs -put HUE_HOME/apps/beeswax/data/sample_07.csv /user/hdfs
$ hdfs dfs -put HUE_HOME/apps/beeswax/data/sample_08.csv /user/hdfs

where HUE_HOME defaultsto /opt/cloudera/parcels/CDH/lib/hue (parcel installation) or /usr/lib/hue
(package installation).

2. Start spark-shell:
$ spark-shell

3. Create Hive tables sample_07 and sample_08:

scala> sqlContext.sql("CREATE TABLE sample_07 (code string,description string,total_emp
 int,salary int) ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t' STORED AS TextFile")
scala> sqlContext.sql("CREATE TABLE sample_08 (code string,description string,total_emp
 int,salary int) ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t' STORED AS TextFile")

Also Read: Learn SparkSQL by your own with little money

 4. In Beeline, show the Hive tables:
[0: jdbc:hive2://hostname.com:> show tables;
+------------+--+
| tab_name |
+------------+--+
16 | Spark Guide
Developing Spark Applications
| sample_07 |
| sample_08 |
+------------+--+

Also read: The role of Spark in Hadoop eco system

5. Load the data in the CSV files into the tables:
scala> sqlContext.sql("LOAD DATA INPATH '/user/hdfs/sample_07.csv' OVERWRITE INTO TABLE
 sample_07")
scala> sqlContext.sql("LOAD DATA INPATH '/user/hdfs/sample_08.csv' OVERWRITE INTO TABLE
 sample_08")

6. Create DataFrames containing the contents of the sample_07 and sample_08 tables:
scala> val df_07 = sqlContext.sql("SELECT * from sample_07")
scala> val df_08 = sqlContext.sql("SELECT * from sample_08")

Apache Spark
7. Show all rows in df_07 with salary greater than 150,000:
scala> df_07.filter(df_07("salary") > 150000).show()
The output should be:
+-------+--------------------+---------+------+
| code| description|total_emp|salary|
+-------+--------------------+---------+------+
|11-1011| Chief executives| 299160|151370|
|29-1022|Oral and maxillof...| 5040|178440|
|29-1023| Orthodontists| 5350|185340|
|29-1024| Prosthodontists| 380|169360|
|29-1061| Anesthesiologists| 31030|192780|
|29-1062|Family and genera...| 113250|153640|
|29-1063| Internists, general| 46260|167270|
|29-1064|Obstetricians and...| 21340|183600|
|29-1067| Surgeons| 50260|191410|
|29-1069|Physicians and su...| 237400|155150|
+-------+--------------------+---------+------+

8.Create the DataFrame df_09 by joining df_07 and df_08, retaining only the code and description columns.
scala> val df_09 = df_07.join(df_08, df_07("code") ===
df_08("code")).select(df_07.col("code"),df_07.col("description"))
scala> df_09.show()

The new DataFrame looks like:
+-------+--------------------+
| code| description|
+-------+--------------------+
|00-0000| All Occupations|
|11-0000|Management occupa...|
|11-1011| Chief executives|
|11-1021|General and opera...|
|11-1031| Legislators|
|11-2011|Advertising and p...|
|11-2021| Marketing managers|
|11-2022| Sales managers|
|11-2031|Public relations ...|
|11-3011|Administrative se...|
|11-3021|Computer and info...|
|11-3031| Financial managers|
|11-3041|Compensation and ...|
|11-3042|Training and deve...|
|11-3049|Human resources m...|
|11-3051|Industrial produc...|
|11-3061| Purchasing managers|
|11-3071|Transportation, s...|
|11-9011|Farm, ranch, and ...|
+-------+--------------------+

9. Save DataFrame df_09 as the Hive table sample_09:
scala> df_09.write.saveAsTable("sample_09")

10. In Beeline, show the Hive tables:
[0: jdbc:hive2://hostname.com:> show tables;
+------------+--+
| tab_name |
+------------+--+
| sample_07 |
| sample_08 |
| sample_09 |
+------------+--+

Comments

Post a Comment

Thanks for your message. We will get back you.

Popular posts from this blog

Step-by-Step Guide to Reading Different Files in Python

-
Image
 In the world of data science, automation, and general programming, working with files is unavoidable. Whether you’re dealing with CSV reports, JSON APIs, Excel sheets, or text logs, Python provides rich and easy-to-use libraries for reading different file formats. In this guide, we’ll explore how to read different files in Python , with code examples and best practices. 1. Reading Text Files ( .txt ) Text files are the simplest form of files. Python’s built-in open() function handles them effortlessly. Example: # Open and read a text file with open ( "sample.txt" , "r" ) as file: content = file.read() print (content) Explanation: "r" mode means read . with open() automatically closes the file when done. Best Practice: Always use with to handle files to avoid memory leaks. 2. Reading CSV Files ( .csv ) CSV files are widely used for storing tabular data. Python has a built-in csv module and a powerful pandas library. Using cs...
Read more

SQL Query: 3 Methods for Calculating Cumulative SUM

-
Image
SQL provides various constructs for calculating cumulative sums, offering flexibility and efficiency in data analysis. In this article, we explore three distinct SQL queries that facilitate the computation of cumulative sums. Each query leverages different SQL constructs to achieve the desired outcome, catering to diverse analytical needs and preferences. Using Window Functions (e.g., PostgreSQL, SQL Server, Oracle) SELECT id, value, SUM(value) OVER (ORDER BY id) AS cumulative_sum  FROM your_table; This query uses the SUM() window function with the OVER clause to calculate the cumulative sum of the value column ordered by the id column. Using Subqueries (e.g., MySQL, SQLite): SELECT t1.id, t1.value, SUM(t2.value) AS cumulative_sum FROM your_table t1 JOIN your_table t2 ON t1.id >= t2.id GROUP BY t1.id, t1.value ORDER BY t1.id; This query uses a self-join to calculate the cumulative sum. It joins the table with itself, matching rows where the id in the first table is greater than...
Read more

PowerCurve for Beginners: A Comprehensive Guide

-
Image
PowerCurve is a complete suite of decision-making solutions that help businesses make efficient, data-driven decisions. Whether you're new to PowerCurve or want to understand its core concepts, this guide will introduce you to chief features, applications, and benefits. What is PowerCurve? PowerCurve is a decision management software developed by Experian that allows organizations to automate and optimize decision-making processes. It leverages data analytics, machine learning, and business rules to provide actionable insights for risk assessment, customer management, fraud detection, and more. Key Features of PowerCurve Data Integration – PowerCurve integrates with multiple data sources, including internal databases, third-party data providers, and cloud-based platforms. Automated Decisioning – The platform automates decision-making processes based on predefined rules and predictive models. Machine Learning & AI – PowerCurve utilizes advanced analytics and AI-driven models ...
Read more