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MCA Articles
Page 93 of 95
Mobile Databases
Mobile databases are separate from the main database and can easily be transported to various places. Even though they are not connected to the main database, they can still communicate with the database to share and exchange data.The mobile database includes the following components −The main system database that stores all the data and is linked to the mobile database.The mobile database that allows users to view information even while on the move. It shares information with the main database.The device that uses the mobile database to access data. This device can be a mobile phone, laptop etc.A communication link ...
Read MoreMultidimensional Databases
Multidimensional databases are used mostly for OLAP (online analytical processing) and data warehousing. They can be used to show multiple dimensions of data to users .A multidimensional database is created from multiple relational databases. While relational databases allow users to access data in the form of queries, the multidimensional databases allow users to ask analytical questions related to business or market trends.The multidimensional databases uses MOLAP (multidimensional online analytical processing) to access its data. They allow the users to quickly get answers to their requests by generating and analysing the data rather quickly.The data in multidimensional databases is stored in ...
Read MoreDate and Time Functions in DBMS
The date and time functions in DBMS are quite useful to manipulate and store values related to date and time.The different date and time functions are as follows −ADDDATE(DATE, DAYS)The numbers of days in integer form (DAYS) is added to the specified date. This is the value returned by the function. For example −sql> SELECT ADDDATE('2018-08-01', 31); +---------------------------------------------------------+ | DATE_ADD('2018-08-01', INTERVAL 31 DAY) | +---------------------------------------------------------+ | 2018-09-01 | +---------------------------------------------------------+ 1 ...
Read MoreSELECT Statement and its Clauses in DBMS
The select statement is used to get the required data from the database according to the conditions, if any. This data is returned in the form of a table.The basic syntax of the select statement is −Select column 1, column 2 ... column N From table_nameAn example of the select statement is −Student_NumberStudent_NameStudent_PhoneStudent_MarksStudent_MajorSubject1Andrew661592728495Literature2Sara658365486565Maths3Harry464756746348Literature4Sally653783708430Literature5Anne745733773288MathsQuery −Select Student_Name From StudentThis query yields the following result −Student_NameAndrewSaraHarrySallyAnneClauses in Select statementThe example of select statement given above is quite simple and not that useful in practice. So, there are many other clauses associated with select statement that make it more meaningful. Some of these are ...
Read MoreLimitations of Database Management System
Database Management System is quite useful compared to the file based management system. However, it does have some disadvantages. Some of those are as follows −More CostlyCreating and managing a database is quite costly. High cost software and hardware is required for the database. Also highly trained staff is required to handle the database and it also needs continuous maintenance. All of these ends up making a database quite a costly venture.High ComplexityA Database Management System is quite complex as it involves creating, modifying and editing a database. Consequently, the people who handle a database or work with it need ...
Read MoreFile-based Data Management System
The systems that are used to organize and maintain data files are known as file based data systems. These file systems are used to handle a single or multiple files and are not very efficient. FunctionalitiesThe functionalities of a File-based Data Management System are as follows −A file based system helps in basic data management for any user.The data stored in the file based system should remain consistent. Any transactions done in the file based system should not alter the consistency property. The file based system should not allow any illegal or potentially hazardous operations to occur on the data.The file based ...
Read MoreWhy do we need a Database
A database is a collection of data, usually stored in electronic form. A database is typically designed so that it is easy to store and access information.A good database is crucial to any company or organisation. This is because the database stores all the pertinent details about the company such as employee records, transactional records, salary details etc.The various reasons a database is important are −Manages large amounts of dataA database stores and manages a large amount of data on a daily basis. This would not be possible using any other tool such as a spreadsheet as they would simply ...
Read MoreObject-oriented Data Model
Object oriented data model is based upon real world situations. These situations are represented as objects, with different attributes. All these object have multiple relationships between them.Elements of Object oriented data modelObjectsThe real world entities and situations are represented as objects in the Object oriented database model.Attributes and MethodEvery object has certain characteristics. These are represented using Attributes. The behaviour of the objects is represented using Methods.ClassSimilar attributes and methods are grouped together using a class. An object can be called as an instance of the class.InheritanceA new class can be derived from the original class. The derived class contains ...
Read MoreSpatial Databases
Spatial data is associated with geographic locations such as cities, towns etc. A spatial database is optimized to store and query data representing objects. These are the objects which are defined in a geometric space.Characteristics of Spatial DatabaseA spatial database system has the following characteristicsIt is a database systemIt offers spatial data types (SDTs) in its data model and query language.It supports spatial data types in its implementation, providing at least spatial indexing and efficient algorithms for spatial join.ExampleA road map is a visualization of geographic information. A road map is a 2-dimensional object which contains points, lines, and polygons ...
Read MoreObject based Data Models
In object based data models, the focus is on how data is represented. The data is divided into multiple entities each of which have some defining characteristics. Moreover, these data entities are connected with each other through some relationships.So, in object based data models the entities are based on real world models, and how the data is in real life. There is not as much concern over what the data is as compared to how it is visualised and connected.Some examples of object based data models areEntity Relationship Data ModelObject Oriented Data ModelSemantic Data ModelFunctional Data ModelOut of these models, ...
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