.NET Tutorials, Forums, Interview Questions And Answers
Welcome :Guest
 
Sign In
Register
 
Win Surprise Gifts!!!
Congratulations!!!


Top 5 Contributors of the Month
david stephan

Home >> Articles >> C# >> Post New Resource Bookmark and Share   

 Subscribe to Articles

What Is a Database?

Posted By:Shashi Ray       Posted Date: March 03, 2009    Points: 25    Category: C#    URL: http://www.dotnetspark.com  
 

What Is a Database?

 

A database is a series of tables of information in some sort of file structure that allows you to access these tables, select columns from them, sort them, and select rows based on various criteria. Databases usually have indexes associated with many of the columns in these tables, so we can access them as rapidly as possible.

 

Databases are used more than any other kind of structure in computing. You'll find databases as central elements of employee records and payroll systems, in travel scheduling systems, and all through product manufacturing and marketing.

 

In the case of employee records, you could imagine a table of employee names and addresses and of salaries, tax withholding, and benefits. Let's consider how these might be organized. You can imagine one table of employee names, addresses, and phone numbers. Other information that

you might want to store would include salary, salary range, last raise, next raise, employee performance ranking, and so forth.

 

Should this all be in one table? Almost certainly not. Salary ranges for various employee types are probably invariant between employees, and thus you would store only the employee type in the employee table and the salary ranges in another table that is pointed to by the type number.

Consider the data in Table.

Key

Lastname

SalaryType

1

Shashi

2

2

Satyam

1

3

Sushil

3

4

Santosh

1

5

Rashmi

2

 

SalaryType

Min

Max

1

30000

45000

2

45000

60000

3

60000

75000

 

 

 

 

 

Table  - Employee Names and Salary Type Tables

 

The data in the SalaryType column refers to the second table. We could imagine many such tables for things like state of residence and tax values for each state, health plan withholding, and so forth. Each table will have a primary key column like the ones at the left of each table and several more columns of data. Building tables in a database has evolved to both an art and a science. The structure of these tables is referred to by their normal form. Tables are said to be in first, second, or third normal form, abbreviated as 1NF, 2NF, or 3NF.

 

·  First. Each cell in a table should have only one value (never an array of values). (1NF)

 

·  Second. 1NF and every non-key column is fully dependent on the key column. This means there is a one-to-one relationship between the primary key and the remaining cells in that row. (2NF)

 

·  Third. 2NF and all non-key columns are mutually independent. This means that there are no data columns containing values that can be calculated from other columns' data. (3NF)

 

Today, nearly all databases are constructed so that all tables are in third normal form (3NF). This means that there are usually a fairly large number of tables, each with relatively few columns of information.

 

Shashi Ray


 Subscribe to Articles

     

Further Readings:

Responses
Author: PankajGupta         Company URL: http://www.dotnetspark.com
Posted Date: July 14, 2009

Can you please tell me which type of database's we can use in .net Platform?

Post Comment

You must Sign In To post reply
Find More Articles on C#, ASP.Net, Vb.Net, SQL Server and more Here

Hall of Fame    Twitter   Terms of Service    Privacy Policy    Contact Us    Archives   Tell A Friend