2/3/2016 notes INSY 3304 - 002
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This 5 page Class Notes was uploaded by loveena Cherukunnathu on Wednesday February 3, 2016. The Class Notes belongs to INSY 3304 - 002 at University of Texas at Arlington taught by Karen Scott in Spring 2016. Since its upload, it has received 40 views. For similar materials see Database Management Systems in Information technology at University of Texas at Arlington.
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Date Created: 02/03/16
Hierarchical and Network Models o Set composed of two record types: • Owner • Member Network model concepts still used today: o Schema Conceptional organization of the database seen by the DBA o Subschema database portion seen by the application programs DML - data management language. We use it to define database environment - ex: how to manipulate data DDL - Data Definition Language. - We use these commands to define the environment, which creates the structure. - ex: creating structure The Relational Model E.F. Codd - father of relational database model - He based his relations as tables Table - A.K.A relations. - Relational model is based on collection of table/relations - Each table represents an entity. - Each table is matrix of rows and columns. Each rows and columns intersect and data can be stored in those. - Each row in a table is referred as a tuple - His model greatly reduced the amount of duplicate data. Relational models were considered impractical in 1970 Simple but a lot of overhead RDBMS - Relational Database Management System - Performs everything as the older models but it hides the complexity from the user. Relational diagram - Representation of the entity, attributes and relationship in a relational database. Relational table - Storing the collection of related entity occurrences. - 1 to many relationship SQL-based relational database application involves three parts: - SQL is the default for relational models o End-user interface what allows user to interact with the data o Set of tables stored in the database Relations/ matrix of rows and columns. Each table is independent from other tables from the database (it can exist alone). In relational database each table should be relate to at least 1 other table. o SQL “engine” SQL engine executes all the quarries. The Entity Relationship Model Widely accepted standard for data modeling Introduced by Chen What does it show? - Graphical representation of the entities and their relationship in a database structure. ERD - Entity relationship diagram. - Each relationship is mapped into a relational table. - This diagrams shows graphical representation of all database components. Entity instance - represents a row in a table or tuple (and that is just a single occurrence of the entity type) Entity set - collection of like entities Connectivity - labels the types of relationship, 1: 1, 1:many, many: many Relationship Expression - Can be notated by using different format o Chen Relationships are represented by diamond shapes, relationship name/description is inside the diamond. o Crowsfoot Relationship is write on, above or below the relationship line. - Entity names are capital and singular - Relationships are in lower case The Object-Oriented (OO) Model Data and relationships are contained in a single structure known as an object - Differentiate OO from others: older models are passive, OO – data is active component. OODM (object-oriented data model) is the basis for OODBMS o Semantic data model An object: o Contains operations o Are self-contained: a basic building-block for autonomous structures o Is an abstraction of a real-world entity Attribute - describe the property of an object Object - an abstraction of real world entity Class - similar objects are grouped into class - Class is organized in a class heritance. Inheritance - is the concepts of objects inheriting methods from parent class UML - Unified Modeling Language - Concepts to describe our oo model with diagrams and symbols. Object/Relational and XML ERDM - extended relational data model - Developed in response to increasing complexity of applications o Semantic data model o Hybrid relational model and OO o O/RDBMS object/relational database management systems o Primarily geared to business applications The Internet revolution created the potential to exchange critical business information XML - Extensible Markup Lang. - allows standard documents to be exchanged on the web. Current databases support XML