The different types of keys in DBMS are −Candidate Key - The candidate keys in a table are defined as the set of keys that is minimal and can uniquely identify any data row in the table.Primary Key - The primary key is selected from one of the candidate keys and becomes the identifying key of a table. It can uniquely identify any data row of the table.Super Key - Super Key is the superset of primary key. The super key contains a set of attributes, including the primary key, which can uniquely identify any data row in the table.Composite Key -  If ... Read More

ER model is used to represent real life scenarios as entities. The properties of these entities are their attributes in the ER diagram and their connections are shown in the form of relationships.Some examples of ER model are −Hospital ER ModelThis is an ER model of a Hospital. The entities are represented in rectangular boxes and are Patient, Tests and Doctor.Each of these entities have their respective attributes which are −Patients - ID(primary key), name, age, visit_dateTests- Name(primary key), date, resultDoctor- ID(primary key), name, specializationThe relationships between different entities are represented by a diamond shaped box.Company ER ModelThe entities in this ... Read More

GeneralizationGeneralization is a process of generalizing an entity which contains generalized attributes or properties of generalized entities. The entity that is created will contain the common features. Generalization is a Bottom up process.We can have three sub entities as Car, Truck, Motorcycle and these three  entities can be generalized into one general super class as Vehicle.It is a form of abstraction that specifies two or more entities (sub class) having common characters that can be generalized into one single entity (super class) at higher level hiding all the differences.SpecializationSpecialization is a process of identifying subsets of an entity that shares ... Read More

EER is a high-level data model that incorporates the extensions to the original ER model. Enhanced ERD are high level models that represent the requirements and complexities of complex database.In addition to ER model concepts EE-R includes −Subclasses and Super classes.Specialization and Generalization.Category or union type.Aggregation.These concepts are used to create EE-R diagrams.Subclasses and Super classSuper class is an entity that can be divided into further subtype.For example − consider Shape super class.Super class shape has sub groups: Triangle, Square and Circle.Sub classes are the group of entities with some unique attributes. Sub class inherits the properties and attributes from ... Read More

A hierarchical model represents the data in a tree-like structure in which there is a single parent for each record. To maintain order there is a sort field which keeps sibling nodes into a recorded manner. These types of models are designed basically for the early mainframe database management systems, like the Information Management System (IMS) by IBM.This model structure allows the one-to-one and a one-to-many relationship between two/ various types of data. This structure is very helpful in describing many relationships in the real world; table of contents, any nested and sorted information.The hierarchical structure is used as the ... Read More

In a "class roster" database, a teacher may teach zero or more classes, while a class is taught by one (and only one) teacher. In a "company" database, a manager manages zero or more employees, while an employee is managed by one (and only one) manager. In a "product sales" database, a customer may place many orders; while an order is placed by one particular customer. This kind of relationship is known as one-to-many.The one-to-many relationship cannot be represented in a single table. For example, in a "class roster" database, we may begin with a table called Teachers, which stores ... Read More

Relational database design (RDD) models’ information and data into a set of tables with rows and columns. Each row of a relation/table represents a record, and each column represents an attribute of data. The Structured Query Language (SQL) is used to manipulate relational databases. The design of a relational database is composed of four stages, where the data are modeled into a set of related tables. The stages are −Define relations/attributesDefine primary keysDefine relationshipsNormalizationRelational databases differ from other databases in their approach to organizing data and performing transactions. In an RDD, the data are organized into tables and all types ... Read More

A database model determines the logical structure of a database and determines in which manner data can be stored, organized and manipulated on a fundamental basis. before the databases are designed, the only way to store data was are in file storage, which increases the complexity as programmers had to go to great lengths to extract the data, and their programs had to perform complex parsing and relating.There are various languages like Perl process the text in an easier manner due to its powerful regular expressions. However, accessing the data from files is still a complex task. There is no ... Read More

The graph is a collection of nodes and edges where each node is used to represent an entity and each edge describes the relationship between entities. A graph-oriented database, or graph database, is a type of NoSQL database that uses graph theory to store, map and query relationships.Graph databases are basically used for analyzing interconnections. For example, companies might use a graph database to mine data about customers from social media.

Now a day, data has been specifically getting stored over clouds also known as a virtual environment, either in a hybrid cloud, public or private cloud. A cloud database is a database that has been optimized or built for such a virtualized environment. There are various benefits of a cloud database, some of which are the ability to pay for storage capacity and bandwidth on a per-user basis, and they provide scalability on demand, along with high availability.A cloud database also gives enterprises the opportunity to support business applications in a software-as-a-service deployment.