Database

A database is basically a collection of information organized in such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic filing system.

Traditional databases are organized by fields, records, and files. A field is a single piece of information; a record is one complete set of fields; and a file is a collection of records. For example, a telephone book is analogous to a file. It contains a list of records, each of which consists of three fields: name, address, and telephone number.

A database management system (DBMS) is a collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMS's, ranging from small systems that run on personal computers to huge systems that run on mainframes

 

Types of Database Management System :->

• Oracle

  Example : Oracle 8, Oracle 9i, Oracle 10g

• MS-SQL Server

  Example : SQL Server 2005, SQL Server 2008

• My-SQL

• MS-Access

  Example : Office 2003, Office 2007,Office 2010, Office 2013
  
  
  

  Database normalization

  Normalization is a database design technique which organizes tables in a manner that reduces redundancy and dependency of data. It divides larger tables to smaller tables and link them using relationships.The inventor of the relational model Edgar Codd proposed the theory of normalization with the introduction of FirstNormal Form and he continued to extend theory with Second and Third Normal Form. Later he joined with Raymond F. Boyce to develop the theory of Boyce-Codd Normal Form.

  
  

  
  

  1st Normal Form (1NF)

  First normal form (1NF) sets the very basic rules for an organized database: Eliminate duplicative columns from the same table. Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).
  

  2nd Normal Form (2NF)

  Second normal form (2NF) further addresses the concept of removing duplicative data: Meet all the requirements of the first normal form. Remove subsets of data that apply to multiple rows of a table and place them in separate tables. Create relationships between these new tables and their predecessors through the use of foreign keys.
  

  3rd Normal Form (3NF)

  Third normal form (3NF) goes one large step further: Meet all the requirements of the second normal form. Remove columns that are not dependent upon the primary key.
  

  4th  Normal Form (4NF)

  If no database table instance contains two or more, independent and multivalued data describing the relevant entity , then it is in 4th Normal Form.
  

  5th  Normal Form (5NF)

  A table is in 5th Normal Form only if it is in 4NF and it cannot be decomposed in to any number of smaller tables without loss of data.
  

  6th  Normal Form (6NF)

  6th Normal Form is not standardized yet however it is being discussed by database experts for some time. Hopefully we would have clear standardized definition for 6th Normal Form in near future.