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RDBMS Articles
Page 5 of 7
Various Types of Keys in DBMS
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 MoreExamples of E-R model
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 MoreOne-to-Many Relationship Model
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 MoreHierarchical Database Model
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 MoreCommercial Database
These are the paid versions of the huge databases designed uniquely for the users who want to access the information for help. These databases are subject specific, and one cannot afford to maintain such a huge information. Access to such databases is provided through commercial links.
Read MoreNoSQL Databases
These are used for large sets of distributed data. There are some big data performance issues which are effectively handled by relational databases, such kind of issues are easily managed by NoSQL databases. There are very efficient in analyzing large size unstructured data that may be stored at multiple virtual servers of the cloud.
Read MoreOperational Database
Information related to operations of an enterprise is stored inside this database. Functional lines like marketing, employee relations, customer service etc. require such kind of databases.
Read MoreCloud Databases
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.
Read MoreEarly Database Models
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 MoreTernary Relationship in Database
In Ternary relationship three different Entities takes part in a Relationship.Relationship Degree = 3For Example: Consider a Mobile manufacture company.Three different entities involved:Mobile - Manufactured by company. Part - Mobile Part which company get from Supplier. Supplier - Supplier supplies Mobile parts to Company.Mobile, Part and Supplier will participate simultaneously in a relationship. because of this fact when we consider cardinality we need to consider it in the context of two entities simultaneously relative to third entity.Cardinality in Ternary RelationshipSay for a given instance of Supplier and an Instance of Part, can that supplier supply that particular part for multiple Mobile models.Example ...
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