Introduction To DBMS Part One

Inspirational-Quotes-2

 

Contributed By: Hosnia Batool 

What is data?

facts and statistics collected together for reference or analysis.Data is also known as raw fact(not processed).

I.e : Name, gender etc.

Data is plural of datum (sing piece of information).

 

what is information?

Information is the result of processed data.Information is also facts provided or learned about something or someone.

 

What is database?

is a collection of related data and data is a collection of facts and figures that can be processed to produce information.

Mostly data represents recordable facts. Data aids in producing information, which is based on facts. For example, if we have data about marks obtained by all students, we can then conclude about toppers and average marks.

data

 

What is DBMS?

Database Management System or DBMS in short refers to the technology of storing and retrieving users’ data with utmost efficiency along with appropriate security measures.It is also a software that allows users to create & maintain a database

.dbms_users

 

What are the types of DBMS?

Well known DBMSs are include  MySQL, PostgreSQL,Microsoft SQL Server, Oracle, Sybase and IBM DB2.

 

What are the types of data model?

There are 3 types of data model:

1) Network   2) Hierarchical   3)Relational

 Network Model:This model organizes data using two fundamental constructs, called records and sets. Records contain fields, and sets define one-to-many relationships between records: one owner, many members.

Hierarchical Model:In this model data is organized into a tree-like structure, implying a single upward link in each record to describe the nesting, and a sort field to keep the records in a particular order in each same-level list.

Relational Model:is a database model based on first-order predicate logic. Its core idea is to describe a database as a collection of predicates over a finite set of predicate variables, describing constraints on the possible values and combinations of values.

 

What is ER diagram?

An entity relationship model, also called an entity-relationship (ER) diagram, is a graphical representation of entities and their relationships to each other, typically used in computing in regard to the organization of data within databases or information systems. An entity is a piece of data-an object or concept about which data is stored.

Relationship between entities: A relationship is how the data is shared between entities.             There are 3 types of relationships between entities:

  • One-to-one:One instance of an entity (A) is associated with one other instance of another entity (B). For example, in a database of employees, each employee name (A) is associated with only one social security number (B).

One-to-one entity relationship diagram

  • One-to-many: One instance of an entity (A) is associated with zero, one or many instances of another entity (B), but for one instance of entity B there is only one instance of entity A. For example, for a company with all employees working in one building, the building name (A) is associated with many different employees (B), but those employees all share the same singular association with entity A.

one to many entity relationship diagram

  • Many-to-many: One instance of an entity (A) is associated with one, zero or many instances of another entity (B), and one instance of entity B is associated with one, zero or many instances of entity A. For example, for a company in which all of its employees work on multiple projects, each instance of an employee (A) is associated with many instances of a project (B), and at the same time, each instance of a project (B) has multiple employees (A) associated with it.

many to many entity relationship diagram

 

 

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