Relational Database Concept

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Relational Database Concept
To understand relation database first lets understand what is data, database & database management system.
DATA : In simple words data can be anything which is relation considerable object. Lets take an Example
Your Name,City, Address is data. another example telephone number is another kind of data.
DataBase : Database is basically a systematic collection of data. Databases permit manipulation or retrieval of their contained data in usable manners.  For Example An online telephone directory would definitely use database to store data related to people, phone numbers, other contact details, etc. There are lots of another example which use database to store the data. Some popular database in programming language are Oracle,SQL Server, MySQL, DB2, Sybase.

Relational Database Concept

A Relational Database management System(RDBMS) is a database management system based on relational model introduced by E.F Codd. In relational model, data is represented in terms of tuples(rows). Relational databases are the most common and frequently used .This type of DBMS defines database relationships in form of tables, also known as relations.MySQL, Oracle, and Microsoft SQL Server database are the example of RDBMS. RDBMS stands for Relational Database Management System. RDBMS follow the Concept Of Normalisation and Denormalisation

Normalisation and Denormalisation

Relational databases use the concept of normalisation. Normalisation is a design technique that reduce the redundancy of data. It also reduces the risk of errors in data caused by copies of the same information not being kept synchronised. By using relationships, the duplication required can be reduced or get rid completely. For example, the database could be created with a single table containing all employees and the details of the department that they have. If two employees have the same department, the department details will be entered twice and must be maintained in two places. By creating a relationship between the employees table and the department table, the department data appears only once and requires updating in only one place. The opposite of normalisation is denormalisation. In a denormalised database information is purposefully duplicated. This provides greater performance than a normalised database at the cost of increased database size and the risk of data integrity problems. Denormalised databases are useful where speed of data retrieval is paramount, such as in a database used for reporting purposes only.

SQL (Strcture Query Language)

Structured Query language (SQL) pronounced as "S-Q-L" or sometimes as "See-Quel"is actually the standard language for dealing with Relational Databases. SQL programming can be effectively used to insert, search, update, delete database records. That doesn't mean SQL cannot do things beyond that. In fact it can do lot of things including, but not limited to, optimizing and maintenance of databases. Relational databases like MySQL Database, Oracle, Ms SQL server, Sybase, etc uses SQL ! How to use sql syntaxes? SQL syntaxes used in these databases are almost similar, except the fact that some are using few different syntaxes and even proprietary SQL syntaxes.
SQL Example
SELECT * FROM Members WHERE Age > 30

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