by • 17/11/2012 • GeneralComments (0)491


A Database is a collection of related and cross-referenced data designed and created to minimize repetition and ease manipulation of data, The data stored in a database are stored in one of the three types of structures i.e. files, tables, or objects.

• A file contains records and fields.

• A table contains rows and columns. In a table, each row contains the same number of columns, and data in the columns are of the same type and size.

• An object consists of both data and methods that act on the data.


Using a database instead of standard flat files has numerous advantages as follows:


1. Data Redundancy reduced

A database reduces data redundancy such that a record appears only once in a database.


2. Data Integrity improved

Since a record appears only once in the database, any changes reflect accordingly.

3. Data Independence maintained

A database maintains data independence such that deleting or changing selected data in a database does not affect other data in the database.


4. Data Security improved

Since most database system maintain ifs own security and all of the data are in one place security is easier to maintain.


5. Data Consistency maintained

A database maintains kind, type, and size of data to be consistent for all applications.


6. Data Manipulation allowed

The data stored in a database can be cross-referenced and integrated; users can perform much more sophisticated data manipulations.


7. Easier Data Access and Use

Since data are available for all applications, the data do not have to be duplicated or repeated, it is easier to access and use it.


Database Query Language

A helpful tool that acts as an interface between users and a relational database management system is called Database Query Language. It helps the users of a relational database to easily manipulate, analyze, and create reports from the data contained in the database. The two basic query styles used in a relational database are query by example and structured query language.


1. Query by Example

In this query style, the database management system displays field information and users enter inquiry conditions in the desire fields.


2. Structured Query Language

It is a standard language for accessing and manipulating databases. It is particularly suitable for searching relational databases. Some common SQL commands include “select”, “insert,” “update,” and “delete”.

A SQL command can:

• execute queries against a database,

• retrieve data from a database,

• insert records in a database,

• update records in a database,

• delete records from a database,

• create new databases,

• create new tables in a database,

• create stored procedures in a database,

• create views in a database,

• set permissions on tables, procedures, and views

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