Basics of JAVA

Welcome to Java!

Java is high level, modern programming language designed in early 1990's by Sun Microsystem, and currently owned by Oracle.

The feature of Java that I like most is Platform Independent i.e. Write Once, Run Anywhere.

More than 3 billion devices run on Java.

Lets suppose someone transfers a file on my laptop with name MyFirstJavaProgram.java(all files with java program written in it has .java extension and is also called source code) and ask me to run on my computer.

Now to run this code on my system, I need few things.

1. Java Development Kit(JDK)
It includes java compiler(javac), java debugging tool(jdb) and java archiving tool(jar).

2. Java Runtime Environment (JRE)
It includes Java Virtual Machine(JVM) and Integrated Development Environment(IDE)
IDE Example - Eclipse

Now you need to set java environment variable path. For this please go through the video with the link below.

https://www.youtube.com/watch?v=oowsJcJLmss

Once the path is set you are ready to run the given code.

What exactly happens?

When you run your .java source code, the java compiler compiles the code and transforms it into bytecode. The file that consists of this bytecode has .class extension.

Now this .class file goes on to JVM(Java Virtual Machine) for execution. Once executed, JVM transforms this bytecode into machine language which our machine understands. The machine language that is created completely depends on your machine(Processor) and its Operating System(Windows, Linux, ..) with which JVM is interacting(that is why it is Platform Dependent, Write Once, Run Anywhere).
 
For an application which consists of multiple java programs, multiple files get created with .class extension. All these files are collected in a single file. This single file is then compressed to easily distribute it over web network to run the application over web. This compressed file has extension .jar(java archive).

In my next blog we will write a simple java program and I will give you some key insights about it. Do follow my blog as it will boost up my morale to write more tutorials. 

Inmon Vs Kimball

Inmon Vs Kimball: Which approach for data warehousing is better?

Firstly, one should know the difference between datawarehouse and data mart.

Data warehouse or Data Mart?

Data Warehouse:

• Holds multiple subject areas
• Holds very detailed information
• Works to integrate all data sources
• Does not necessarily use a dimensional model(denormalized data model) but generally feeds dimensional models.

Data Mart

• Often holds only one subject area- for example, Finance, or Sales
• May hold more summarised data (although many hold full detail)
• Concentrates on integrating information from a given subject area or set of source systems
• Is built focused on a dimensional model using a star schema.
 

 

Bill Inmon's paradigm: 

Data warehouse is one part of the overall business intelligence system. An enterprise has one data warehouse, and data marts source their information from the data warehouse. In the data warehouse, information is stored in 3rd normal form. Data Marts are physical.

Data Warehouse –Normalized Data Model in 3NF

 

 

 Ralph Kimball's paradigm:

Data warehouse is the conglomerate of all data marts within the enterprise. Information is always stored in the dimensional model. Data Marts are Logical(Views).

Data Warehouse –De-normalized Dimensional Data Model

 

Misconception:

Actually, there is no right or wrong between these two ideas, as they represent different data warehousing philosophies. In reality, the data warehouse systems in most enterprises are closer to Ralph Kimball's idea. This is because most data warehouses started out as a departmental effort, and hence they originated as a data mart. Only when more data marts are built later do they evolve into a data warehouse.  

Likewise, most people working in Data Warehousing would rather skip the Data Warehouse and go straight to the Data Mart.

In Industry, people often claims to be one of these methodologies, however, often they are using a combination of parts of two or more, usually all three!