DATABASE & SQL/PLSQL

DATABASE MODELS
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Relational Database Model

Data represent in form of column and row, column means attribute and row means touples present instance of data. This Database model came into existence with help of mathematical concepts. Its using some other concepts like normalization, touple relational calculus.

E-R Model in Database

E-R model stands for Entity-Relationship model. This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entity in database, which existence in real world with number of attributes. In a table attribute know as column. Relationship is a logical thing which relates entities. The E-R diagram shows structure of E-R model.

 

Object Oriented Database Model

This model is based on collection of objects. An object is instance variables which store value and bodies of code, that codes are called method. These codes have written to operate the objects. Objects that contain same types of values and the same methods are grouped together into classes. In other words classes are a group of object. This model also follows the some concept related to the OOPs

Hierarchical model of Database

The word hierarchy means tree form relationship, like a tree with branches. Means Relationship formed like tree structure in a database called hierarchical model. With this database you form relationship among many tables with certain concept. It has a downward link to describe the nesting and they are arranged in a particular order down the same level of the list.

Network model

This model provides greater flexibility and easy access to data. This model provide logical relationship among many parent database. But implementing this model is more difficult due to time consuming and cost. Its flexible because through link easily accessing of information.

XML Database

XML databases came into existence in 2000. This database lets you organize data irrespective of whether it is organized or not. This data can exported and serialized into the desired format. Two major classes of XML database exist:

  1. XML-enabled
  2. Native XML
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