Data Dictionary consists of database metadata. It has records about objects in the database.What Data Dictionary consists ofData Dictionary consists of the following information −Name of the tables in the databaseConstraints of a table i.e. keys, relationships, etc.Columns of the tables that related to each otherOwner of the tableLast accessed information of the objectLast updated information of the objectAn example of Data Dictionary can be personal details of a student −ExampleStudent_IDStudent_NameStudent_AddressStudent_CityThe following is the data dictionary for the above fields −Types of Data DictionaryHere are the two types of data dictionary −Active Data DictionaryThe DBMS software manages the active data ... Read More

Entity in DBMS can be a real-world object with an existence. To identify entity from a given problem, follow the below given tips −Under the problem description, try to find the entity.Search for nouns, like Teacher, Doctor, etc.Classify nouns to get a wider picture about the entities.Read the problem description repeatedly.Entities are like Persons, Students, Teachers, Courses.Entities has attributes, that properties describing it, for example, for Professor entity, the attributes are  Professor_Name, Professor_Address, Professor_Salary, etcFor example, Problem DescriptionHospital has doctors and patients. Patients visit the hospital to get a consultation from the doctor. Doctor may suggest tests to examine the condition ... Read More

Database Design Methodologies has phases to guide the designer for assistance. The Methodology has a structured approach to help in the design process.The following are the phases/ models −Conceptual PhaseThe Conceptual phase lets you know the entities and the relation between them. It describes the conceptual schema. The entities & relations are defined here.Logical PhaseLogical data model provides details about the data to the physical phase. The physical process gives ER Diagram, data dictionary, schema, etc that acts as a source for the physical design process.Physical PhaseThe physical database design allows the designer to decide on how the database will ... Read More

A good database design has many benefits and is a goal to achieve for every DBA −Easy Retrieval of InformationIf the design is developed properly, then it would be easier to retrieve information. Correct design means the tables, constraints, and relationships created are flawless.Easier ModificationChanges that you make to the value of a given field will not adversely affect the values of other fields within the table.Easy to MaintainThe database structure should be easy to maintain. The design is perfect if changes in one field is not affecting changes in another field.InformationWith a good design, you can enhance the quality ... Read More

Many-to-Many relationship in DBMS is a relationship between more than one instance of an entity with more than one instance of another entity i.e. both the entities can have many relationships between each other.The relation can be stated as −Let us see an example −Many Authors can write a Book, whereas an Author has written more than one book.Here, Book and Author are entities.Let’s say a book has two authors, whereas an individual author has written six books till now.

An attribute is fully functional dependent on another attribute, if it is Functionally Dependent on that attribute and not on any of its proper subset.For example, an attribute Q is fully functional dependent on another attribute P, if it is Functionally Dependent on P and not on any of the proper subset of P.Let us see an example −ProjectIDProjectCost00110000015000EmpIDProjectIDDaysE099001320E056002190The above relations states that −Days are the number of days spent on the project.EmpID, ProjectID, ProjectCost -> DaysHowever, it is not fully functional dependent.Whereas the subset {EmpID, ProjectID} can easily determine the {Days} spent on the project by the employee.This summarizes ... Read More

Database Design can be a tiresome task and you would need to follow the below approach and tackle the challenges to get a well-designed database.The concerns and challenges with Database design are the following −Following Design StandardsConsidering Design Standards while designing a database is quite essential. It gives you components that are well defined. With this, you can also easily evaluate an existing design.If you are unable to follow the design standards approach, then do not expect the design to be proper and you will not be able to evaluate it.Achieving High Processing SpeedEveryone needs faster access for the relationships ... Read More

Relationships in DBMS can be stated as a relation between two entities like Employee-Department, Student-Course, etc.One-to-One relationship in DBMS is a relationship between an instance of an entity with another.The relation can be stated as −An Employee is issued an Employee ID Card. An individual employee is offered a unique ID card in the company. Here, Employee and ID Card (ID_Card) are entities.

Managing data was the key and was essential. Therefore, data model originated to solve the file system issues. Here are the Data Models in DBMS −Hierarchical ModelIn Hierarchical Model, a hierarchical relation is formed by collection of relations and forms a tree-like structure.The relationship can be defined in the form of parent child type.One of the first and most popular Hierarchical Model is Information Management System (IMS), developed by IBM.ExampleThe hierarchy shows an Employee can be an Intern, on Contract or Full- Time. Sub-levels show that Full-Time Employee can be hired as a Writer, Senior Writer or Editor:AdvantagesThe design of ... Read More

Good Database Design is what everyone wants to achieve to avoid the consequences of dealing with a bad design.The following are the objectives of a good database design −Avoid Redundant DataThe table in the database should be constructed following standards and with utmost dedication. It should have different fields and minimize redundant data. The table should always have a Primary Key that would be a unique id.Faultless InformationThe database should follow the standards and conventions and provide meaningful information useful to the organization.Data IntegrityIntegrity assists in guaranteeing that the values are valid and faultless. Data Integrity is set to tables, ... Read More