Found 1719 Articles for Big Data Analytics

In the 2NF, relation must be in 1NF. In the second normal form, all the non-key attributes are fully functional dependent on the primary key. Or a relation is in 2NF, when it is in 1NF and there is no partial dependency.ExampleConsider a relation R (rollno, name, subjectcode, subjectname, duration)RollnoNameSubjectcodeSubjectnameDuration1HariS1C60 days1HariS2Java90 days2PinkyS1C60 days2PinkyS2Java90 days3RakhiS3Database45 daysF: {rollno -> name, subjectcode -> (subjectname, duration).{rollno, subjectcode}+ = {rollno, name, subjectcode, subjectname, duration}=> {rollno, subjectcode } is candidate key.The above table is in 1NF because no multivalued attributes are present. But it is not in 2NF because the following two partial dependencies are present.Rollno->name ... Read More

The three-schema architecture divides the database into three-level used to create a separation between the physical database and the user application. In simple terms, this architecture hides the details of physical storage from the user.The database administrator (DBA) responsible is to change the structure of database storage without affecting the user’s view. It deals with the data, the relationship between them and the different access methods implemented on the database. The logical design of a database is called a schema.This architecture contains three layers of database management system (DBMS) −External levelConceptual levelInternal levelThe three layers of the DBMS are pictorially ... Read More

Attributes are the properties which describe an entity. Example The attributes of student entity are as follows − Roll number Name Branch Age Types of attributes The different types of attributes are as follows − Composite attribute It can be divided into smaller sub parts, each sub part can form an independent attribute. For example −     ... Read More

Data independence is the ability to modify the scheme without affecting the programs and the application to be rewritten. Data is separated from the programs, so that the changes made to the data will not affect the program execution and the application.We know the main purpose of the three levels of data abstraction is to achieve data independence. If the database changes and expands over time, it is very important that the changes in one level should not affect the data at other levels of the database. This would save time and cost required when changing the database.There are two ... Read More

The three-schema architecture divides the database into three-level used to create a separation between the physical database and the user application. In simple terms, this architecture hides the details of physical storage from the user.The database administrator (DBA) responsible is to change the structure of database storage without affecting the user’s view. It deals with the data, the relationship between them and the different access methods implemented on the database. The logical design of database is called a schemaThis architecture contains three layers of database management system, which are as follows −External levelConceptual levelInternal levelExternal/ View levelThis is the highest ... Read More

If a non-key attribute(s) depends on a part of a candidate key then it is partial dependency, it is applicable where the primary key has multiple attributes. If a non-key attribute(s) depends on the entire candidate key, then it is full dependency.Example 1Let R(A, B, C) and AB=candidate key.A-> C is a partial dependency (where C dependson a part of the candidate key).AB->C is a full dependency (where c depends on the entire candidate key).A Functional dependency X->Y is a partial dependency if, X is a part of candidate key andY is a non-key attribute(s).Example 2R(ABCDE)F: {AB->C, C->D, B->E }. ... Read More

The real-world problems are closely represented through the object-oriented data model.In this type of model, both the data and relationship are represented in a single structure called an object.We can store audio, video, images, etc. in this database, but it is advised not to store in the relational database. In this model, the attributes describe the properties of an object.Objects that share similar characteristics are grouped in classes. Therefore, a class is a collection of similar objects with attributes and methods. In this model, two or more objects are connected with the help of links. We use this link to ... Read More

In relational models, the data is maintained in the form of a two-dimensional table.Information is stored in the form of rows and columns. The basic structure of this model is tables. Generally, tables are called relations in the relational model.ExampleLet’s consider a student tableStd-IdStd-NameAgeBranch101Hari20CSE102Pinky22EEE103Bob20CSE104Lucky21ECEFeaturesThe features of Relational Model are as follows −Tuples − Each row in the table is called a tuple. A row contains all the information about any instance of the object. In the above example, each row contains all the information regarding each student.Attribute or field − Attributes are property which defines the table or relation. The ... Read More

A relation is in 1NF if it contains atomic values. It states that an attribute of a table cannot hold multiple values. It must hold only single-values attributes. First normal form disallows the multi-valued attributes, composite attributes, and their combinations.RequirementsThe requirements to be considered while designing 1 NF are explained below −Each table has a primary key (minimal set of attributes which can uniquely identify a record).The values in each column of a table are atomic (no multi0value attributes are allowed).There are no repeating groups (two columns do not store similar information in the same table).Example 1Consider a relation student ... Read More

Entity relationship (ER) models are based on the real-world entities and their relationships. It is easy for the developers to understand the system by simply looking at the ER diagram. ER models are normally represented by ER-diagrams.ComponentsER diagram basically having three components:Entities − It is a real-world thing which can be a person, place, or even a concept. For Example: Department, Admin, Courses, Teachers, Students, Building, etc are some of the entities of a School Management System.Attributes − An entity which contains a real-world property called an attribute. For Example: The entity employee has the property like employee id, salary, ... Read More