Skip to main content

Posts

Showing posts from 2014

The Year 1970........

The Year 1970.....

This was one of the fabulous years in the history of Computers when one of the best inventions of Computers took place,

1. RDBMS by EF Codd
2. C by Dennis Ritchie

C was first implemented by Dennis Ritchie on a DEC PDP-11 running on Unix OS. C was the result of an older Language BCPL developed by Martin Richards and later took a transformation and led to the birth of language B by Ken Thompson inturn leading to development of C by Dennis.

The first book on C was released by Prentice-Hall in 1978 by Kernighan and Dennis Ritchie with the name The C Programming Language.

C was finally standardized in December 1989 when ANSI adopted the standard for C and was know as programmers language designed by and for programmers.

This transformation in the field of Programing languages started with language BASIC, COBOL and then to FORTRAN and to more structured programming language PASCAL.

All this transformation led to the creation of C++ which is a direct descendent of C and then C+…

SQL Query to find number of columns of a table

I have been receiving lots of mails on how to find number of columns of a table without using DESCRIBE command or using a statement.

This is very simple, you just have to know another Data Dictionary Table USER_TAB_COLUMNS.

SELECT count(*)
from USER_TAB_COLUMNS
where table_name = 'EMP';





Happy Reading........

Converting Rows to Single Column

Strange solution for someone who is looking into this statement for the first time.

I have used XMLAGG, XMLELEMENT and EXTRACT functions. See if you can crack it.


XMLAGG is an aggregate/group function which aggregates all the values for a column.
XMLELEMENT is a function which creates XML tags with tag element E.
EXTRACT function then removes all the XML text and retains only text.

SELECT   deptno,  XMLAGG (XMLELEMENT (e, ename || ',')).EXTRACT ('//text()') as ENAMES
FROM
   emp
GROUP BY deptno;

This statement will give you an output as below,







If you observe in this output, there is an extra comma at the end of the ENAMEs list. To remove this, I shall use another function RTRIM which is used to trim characters on the right side.

SELECT   deptno,  RTRIM(XMLAGG (XMLELEMENT (e, ename || ',')).EXTRACT ('//text()'),',') as ENAMES
FROM
   emp
GROUP BY deptno;







In case if the output does not show the values properly then use the following command to restrict t…

Finding Leap Year using SQL

Before we start writing a statement to find a Leap Year, let us first understand what is a Leap Year.

According to Gregorian Calendar each year consists of 365 day. In reality Earth takes approximately 365.242375 days to circle once around the Sun.

As the Gregorian calendar has only 365 days in a year, so if we didn't add a day on February 29 nearly every 4 years, we would lose almost six hours off our calendar every year. After only 100 years, our calendar would be off by approximately 24 days!

Lets look at it in more details,

Because the Earth rotates about 365.242375 times a year ...

... but a normal year is 365 days, ...

... so something has to be done to "catch up" the extra 0.242375 days a year.

So every 4th year we add an extra day (the 29th of February), which makes 365.25 days a year. This is fairly close, but is wrong by about 1 day every 100 years.

So every 100 years we don't have a leap year, and that results in 365.24 days per year (1 day less in 100 ye…

Cloud Computing

Cloud is a new concept of networking based on something called as Virtualization. Using this concept of Virtualization to provide different kinds of services to Users, small scale to large scale companies.




These services are mainly classified into,

1. SaaS -- Software as a Service
2. PaaS -- Platform as a Service
3. IaaS -- Infrastructure as a Service
4. HaaS -- Hardware as a Service

Cloud makes any service available online making users access everything that they need with few clicks.

To understand better, following is a youtube video from IBM's BlueMix Cloud. You can watch this video and see that its so simple to have your own site created on a server to which you can choose hardware configurations.

Enjoy the Video from IBM BlueMix -- CLICK HERE

Also refer to Wiki link for more details and History -- Click Here

Happy Learning.

Basics of Unix/Linux

Like Networking even Basics of Unix or Linux Knowledge will help get a better job.

Refer to the links below for knowledge on Unix and Linux,

http://www.ee.surrey.ac.uk/Teaching/Unix/

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/basics.html

http://en.wikipedia.org/wiki/Linux

Enjoy your reading.

Basics of Networking

In DBMS first thing that any one should know is Client Server Architecture. This is not only true for DBMS but for anyone in IT should have basic knowledge of networking.

You can read about basics of networking from the links below.

www.unt.edu/zlot/survey/client_server_krm_01may2002.ppt

http://www.indiabix.com/technical/networking/3

http://www.mhprofessional.com/downloads/products/0071615385/0071615385_chap01.pdf  

http://en.wikipedia.org/wiki/OSI_model

http://en.wikipedia.org/wiki/TCP/IP_model

Enjoy your reading.

PL/SQL and Microsoft Excel Details

You can download the book for PL/SQL from the link below,

PLSQL -- http://docs.oracle.com/cd/B19306_01/appdev.102/b14261/toc.htm
In the above link, be through in first 2 chapters.
For Excel, First go through first link below,

1. http://www.bamaed.ua.edu/tutorial/itrc/excel/excel.htm

Above link should not take more than 40 mins to complete.

Once you are done with the first link, learn how to create a Pie chart from the link below

2. http://office.microsoft.com/en-in/excel-help/basic-tasks-in-excel-2013-HA102813812.aspx

Go through the video below on excel,

3. https://www.youtube.com/watch?v=rJbf-2XXsuY