The document discusses the entity-relationship (E-R) model for database design. It describes entity sets as collections of entities of the same type that share attributes. Relationship sets define associations among entity sets. The E-R diagram uses graphical symbols like rectangles, diamonds, and lines to represent entity sets, relationship sets, and attributes. It also covers relationship cardinalities, roles, participation constraints and other E-R modeling concepts for conceptual database design.
The document provides an overview of relational database concepts and the Oracle database implementation. It describes the life cycle development phases, theoretical and conceptual aspects of relational databases, and how SQL is used with Oracle's RDBMS and ORDBMS. It also covers basic SQL statements like SELECT and restrictions, data types, database objects, SQL statements, operators, and comparisons that can be used with SQL.
The document discusses the Entity-Relationship (ER) model for database design. It describes the ER model as having three phases: conceptual, logical, and physical design. The conceptual design produces an initial model of the application domain using the ER model. This model is then transformed into the logical relational model supported by the database management system. Physical design then optimizes performance. The document outlines the basic constructs of the ER model including entities, attributes, relationships, and how they are depicted in ER diagrams.
A great power point presentation for DBMS Concepts from start to end and with best examples chapter by chapter. Please go though each chapters sequentially for your knowledge.
A very easy going study material for better understanding and concepts of Database Management System.
03 fsm how_toimplementai_state_20161006_jintaeksJinTaek Seo
This document discusses modeling game objects using finite state machines and state diagrams. It provides an example of modeling a monster's states which include idle, moving, attack, hurt, and dead. The modeling process involves two steps: 1) creating an object state diagram to represent the states and transitions, and 2) implementing the model in a game client. Additional sub-states like crawl, walk and run can be added to the moving state. The document also provides an example of implementing a simple desktop calculator using state machines and discusses how to identify the states for the calculator problem.
Entity relationship diagrams (ERDs) are a graphical representation of entities and their relationships in a database. ERDs were developed in 1976 by Peter Chen and introduced by Charles Bachman. An ERD uses objects, attributes, and relationships to model how data is connected. Relationships can be one-to-one, one-to-many, or many-to-many. Cardinality and modality are also expressed to define maximum numbers and whether relationships are optional or mandatory.
This document discusses the components of an entity-relationship diagram including entities, attributes, relationships, and constraints. An entity-relationship diagram is a conceptual data model that shows entities, attributes, and relationships. The diagram defines entities, attributes, and three types of relationships: one-to-one, one-to-many, and many-to-many. It also covers cardinality and participation constraints that specify the minimum and maximum number of relationships allowed.
entity relationship diagram or ERD is always required while starting any database project. myassignmenthelp provides help with all kinds of such assignments.
The document provides an overview of relational database concepts and the Oracle database implementation. It describes the life cycle development phases, theoretical and conceptual aspects of relational databases, and how SQL is used with Oracle's RDBMS and ORDBMS. It also covers basic SQL statements like SELECT and restrictions, data types, database objects, SQL statements, operators, and comparisons that can be used with SQL.
The document discusses the Entity-Relationship (ER) model for database design. It describes the ER model as having three phases: conceptual, logical, and physical design. The conceptual design produces an initial model of the application domain using the ER model. This model is then transformed into the logical relational model supported by the database management system. Physical design then optimizes performance. The document outlines the basic constructs of the ER model including entities, attributes, relationships, and how they are depicted in ER diagrams.
A great power point presentation for DBMS Concepts from start to end and with best examples chapter by chapter. Please go though each chapters sequentially for your knowledge.
A very easy going study material for better understanding and concepts of Database Management System.
03 fsm how_toimplementai_state_20161006_jintaeksJinTaek Seo
This document discusses modeling game objects using finite state machines and state diagrams. It provides an example of modeling a monster's states which include idle, moving, attack, hurt, and dead. The modeling process involves two steps: 1) creating an object state diagram to represent the states and transitions, and 2) implementing the model in a game client. Additional sub-states like crawl, walk and run can be added to the moving state. The document also provides an example of implementing a simple desktop calculator using state machines and discusses how to identify the states for the calculator problem.
Entity relationship diagrams (ERDs) are a graphical representation of entities and their relationships in a database. ERDs were developed in 1976 by Peter Chen and introduced by Charles Bachman. An ERD uses objects, attributes, and relationships to model how data is connected. Relationships can be one-to-one, one-to-many, or many-to-many. Cardinality and modality are also expressed to define maximum numbers and whether relationships are optional or mandatory.
This document discusses the components of an entity-relationship diagram including entities, attributes, relationships, and constraints. An entity-relationship diagram is a conceptual data model that shows entities, attributes, and relationships. The diagram defines entities, attributes, and three types of relationships: one-to-one, one-to-many, and many-to-many. It also covers cardinality and participation constraints that specify the minimum and maximum number of relationships allowed.
entity relationship diagram or ERD is always required while starting any database project. myassignmenthelp provides help with all kinds of such assignments.
C:\documents and settings\student\desktop\swaroop umlsatyaiswaroop
The document provides an overview of use case modeling, state machines, and activity diagrams in UML. It describes core concepts of use case modeling including use cases, actors, and relationships. It also covers when to use use case modeling and provides tips. An example online HR system use case diagram is shown. State machine concepts like states, transitions, entry/exit actions, and hierarchical state machines are explained.
Dokumen tersebut membahas tentang state machine diagram yang digunakan untuk menggambarkan perilaku suatu sistem. State machine diagram menampilkan state, event, dan transisi yang mungkin terjadi pada suatu objek. Diagram ini berisi simbol, aktivitas, dan konsep seperti guard condition dan composite state.
Three state transition diagram flow chart slides power pointSlideTeam.net
The document describes how to edit images in PowerPoint presentations. It shows a three state transition diagram with steps to edit images. Images can be ungrouped to edit individual elements. Colors can be changed by right clicking the image and selecting format shape or by using theme colors from the design tab. The document provides instructions on editing colors, size, and orientation of images to customize PowerPoint presentations.
An entity relationship diagram (ERD) shows the relationships between entities in a database. The document provides two examples of ERDs - one for a supplier/parts database and another for a doctor's office managing branches, GPs, patients, and appointments. For each ERD, the entities are identified and then linked with identifying relationships and assumptions stated. Alternative layouts for ERDs are also discussed.
In software engineering, an entity–relationship model (ER model) is a data model for describing the data or information aspects of a business domain or its process requirements
The document describes the steel making process and its entity relationship diagram. The major steps in steel making are: coke oven, blast furnace, LD converter, secondary refining, and casting. Raw materials like iron ore, coal, and limestone are transformed through these steps into finished steel products like slabs, bars, and coils. The entity relationship diagram shows the relationships between vendors, raw materials, finished steel, products, and customers in the steel making process.
UML state machine diagrams depict the states an object can be in and the transitions between those states. States are represented by rounded rectangles with transition lines connecting them. Initial states have filled circles while final states have empty circles with dots. Transitions can have triggers, guards, and effects associated with them. Self-transitions allow an object to return to the same state. Superstates group common transitions to simplify diagrams. Compound states include submachine diagrams. Pseudo-states like choices and junctions control transitions. Concurrent regions divide states into concurrently executing parts using fork and join pseudo-states.
The document provides information on entity relationship diagrams (ERDs), including their objectives, components, and how to construct them. An ERD is a graphical representation of entities, attributes, and relationships within a database. It serves as a design tool, documentation, and means to communicate the logical structure. Key aspects covered include identifying entities and attributes, defining relationships and cardinalities, and using standard symbols and notations to draw the ERD.
This document discusses entity relationship diagrams (ERDs), which are used to model databases and their logical structure. It defines key terms like entities, attributes, relationships, and cardinality. It explains that ERDs show entities as rectangles, relationships as diamonds, and cardinalities with notation like one-to-one. The document outlines the steps to create an ERD, including identifying entities, attributes, relationships, and cardinalities, then drawing the diagram. It provides examples of one-to-one, one-to-many, and many-to-many relationships.
State chart diagrams describe the different states an object can be in, the transitions between states, and activities that occur during an object's lifetime. A state diagram models the transitions within a single class in response to events. Elements include initial and final states, states, transitions between states indicating triggers and guards, and pseudostates. Common pseudostates include choices, histories, junctions, entry/exit points, and terminate. State diagrams are useful for modeling workflows, document processing, real-time applications, and the behavior of a class over multiple use cases.
Entity Relationship Diagram Templates by CreatelyCreately
Creately offers many ER (Entity Relationship) Diagram templates which you can use instantly to create your own diagrams. Simple ER diagrams to the most complex system ER diagram templates can be found on our diagram community, template just click on the use as templates button to immediately start modifying it using our online diagramming tools.
Entity relationship diagram - Concept on normalizationSatya Pal
The document discusses database normalization from the entity relationship diagram stage through fifth normal form. It describes how entities from the ER diagram become tables and how relationships are modeled. Anomalies in unnormalized relations are explained, along with how different normal forms address these issues. The document also discusses denormalization techniques used to improve query performance and some limitations of normalization.
Entity Relationship Diagrams (ERDs) are used to model relationships between entities in a database. The document discusses ERD components like entities, relationships, cardinality, and attributes. It provides an example of an ERD for a company with departments, supervisors, employees, and projects. Key entities are identified and their relationships and attributes are represented in the example ERD diagrams.
The document provides an overview of entity relationship diagrams (ERDs) including their basic components, different notations, and how to implement various relationship types in a relational database. ERDs depict entities, attributes, and relationships in a conceptual database design. Key points covered include the three main notations of ERDs, solving multi-valued attributes and many-to-many relationships, and how to implement one-to-one, one-to-many, and many-to-many relationships through primary and foreign key constraints.
The document discusses the entity-relationship (E-R) data model. It defines key concepts in E-R modeling including entities, attributes, entity sets, relationships, and relationship sets. It describes different types of attributes and relationships. It also explains how to represent E-R diagrams visually using symbols like rectangles, diamonds, and lines to depict entities, relationships, keys, and cardinalities. Primary keys, foreign keys, and weak entities are also covered.
The document discusses software design concepts and the Unified Modeling Language (UML). It introduces software design as translating requirements into a blueprint for constructing software. Key concepts discussed include abstraction, architecture, patterns, modularity, information hiding, and refinement. The document also explains UML's use for visual modeling through diagrams like use case diagrams, class diagrams, and state machine diagrams. It describes how UML can be used across the software development lifecycle.
The document discusses entity relationship diagrams and database design. It defines key concepts such as entities, attributes, relationships and cardinalities. Entities can have single-valued or multi-valued attributes. Relationships connect entities and can be one-to-one, one-to-many, many-to-one, or many-to-many. Primary keys uniquely identify entities and foreign keys define relationships between entities. Together these elements form a conceptual model of entities and their relationships within a database.
The document provides an overview of entity-relationship (E-R) modeling concepts including:
- Entity sets represent collections of real-world entities that share common properties
- Relationship sets define associations between entity sets
- Attributes provide additional information about entities and relationships
- Keys uniquely identify entities and relationships
- Cardinalities constrain how entities can participate in relationships
- E-R diagrams visually depict entity sets, attributes, relationships and constraints.
The document discusses state modeling and state diagrams. It defines states as representations of intervals of time that describe an object's behavioral condition. Events trigger transitions between states. A state diagram uses a graph to represent an object's states and the transitions between them caused by events. It specifies the object's response to input events over time. The document provides examples of how to notationally represent states, transitions, events, and other elements in a state diagram.
The document provides information on entity relationship diagrams (ERDs), including the objectives, components, and steps to create an ERD. It defines key ERD concepts like entities, attributes, relationships, and cardinality. It describes the entity modeling process and discusses how to recognize entities, attributes, relationships, and cardinalities in a database. It outlines the general steps to create an ERD, including identifying entities, finding relationships between entities, drawing a rough ERD, defining primary keys, identifying attributes, mapping attributes to entities, and drawing a fully attributed ERD. Sample ERDs are provided to illustrate concepts like cardinality constraints.
The document discusses entity-relationship (E-R) modeling concepts used to design databases. It defines entity sets as collections of entities that share common properties and attributes. Relationship sets describe associations between entity sets. E-R diagrams graphically represent entity sets as rectangles, relationship sets as diamonds, and attributes as ellipses linked to the appropriate sets. The document also covers mapping cardinalities between entity sets, roles that clarify relationships, and cardinality constraints depicted in E-R diagrams. The goal of E-R modeling is to design an E-R schema to logically represent entities, attributes, and relationships in a database.
The document provides information about database management systems and the relational database model. It discusses data models, entity relationship modeling, relational databases, normalization of database tables, and relational database design. Key topics covered include the entity relationship model, E-R diagrams, relationship sets, attributes, keys, normalization forms, and designing normalized database tables.
C:\documents and settings\student\desktop\swaroop umlsatyaiswaroop
The document provides an overview of use case modeling, state machines, and activity diagrams in UML. It describes core concepts of use case modeling including use cases, actors, and relationships. It also covers when to use use case modeling and provides tips. An example online HR system use case diagram is shown. State machine concepts like states, transitions, entry/exit actions, and hierarchical state machines are explained.
Dokumen tersebut membahas tentang state machine diagram yang digunakan untuk menggambarkan perilaku suatu sistem. State machine diagram menampilkan state, event, dan transisi yang mungkin terjadi pada suatu objek. Diagram ini berisi simbol, aktivitas, dan konsep seperti guard condition dan composite state.
Three state transition diagram flow chart slides power pointSlideTeam.net
The document describes how to edit images in PowerPoint presentations. It shows a three state transition diagram with steps to edit images. Images can be ungrouped to edit individual elements. Colors can be changed by right clicking the image and selecting format shape or by using theme colors from the design tab. The document provides instructions on editing colors, size, and orientation of images to customize PowerPoint presentations.
An entity relationship diagram (ERD) shows the relationships between entities in a database. The document provides two examples of ERDs - one for a supplier/parts database and another for a doctor's office managing branches, GPs, patients, and appointments. For each ERD, the entities are identified and then linked with identifying relationships and assumptions stated. Alternative layouts for ERDs are also discussed.
In software engineering, an entity–relationship model (ER model) is a data model for describing the data or information aspects of a business domain or its process requirements
The document describes the steel making process and its entity relationship diagram. The major steps in steel making are: coke oven, blast furnace, LD converter, secondary refining, and casting. Raw materials like iron ore, coal, and limestone are transformed through these steps into finished steel products like slabs, bars, and coils. The entity relationship diagram shows the relationships between vendors, raw materials, finished steel, products, and customers in the steel making process.
UML state machine diagrams depict the states an object can be in and the transitions between those states. States are represented by rounded rectangles with transition lines connecting them. Initial states have filled circles while final states have empty circles with dots. Transitions can have triggers, guards, and effects associated with them. Self-transitions allow an object to return to the same state. Superstates group common transitions to simplify diagrams. Compound states include submachine diagrams. Pseudo-states like choices and junctions control transitions. Concurrent regions divide states into concurrently executing parts using fork and join pseudo-states.
The document provides information on entity relationship diagrams (ERDs), including their objectives, components, and how to construct them. An ERD is a graphical representation of entities, attributes, and relationships within a database. It serves as a design tool, documentation, and means to communicate the logical structure. Key aspects covered include identifying entities and attributes, defining relationships and cardinalities, and using standard symbols and notations to draw the ERD.
This document discusses entity relationship diagrams (ERDs), which are used to model databases and their logical structure. It defines key terms like entities, attributes, relationships, and cardinality. It explains that ERDs show entities as rectangles, relationships as diamonds, and cardinalities with notation like one-to-one. The document outlines the steps to create an ERD, including identifying entities, attributes, relationships, and cardinalities, then drawing the diagram. It provides examples of one-to-one, one-to-many, and many-to-many relationships.
State chart diagrams describe the different states an object can be in, the transitions between states, and activities that occur during an object's lifetime. A state diagram models the transitions within a single class in response to events. Elements include initial and final states, states, transitions between states indicating triggers and guards, and pseudostates. Common pseudostates include choices, histories, junctions, entry/exit points, and terminate. State diagrams are useful for modeling workflows, document processing, real-time applications, and the behavior of a class over multiple use cases.
Entity Relationship Diagram Templates by CreatelyCreately
Creately offers many ER (Entity Relationship) Diagram templates which you can use instantly to create your own diagrams. Simple ER diagrams to the most complex system ER diagram templates can be found on our diagram community, template just click on the use as templates button to immediately start modifying it using our online diagramming tools.
Entity relationship diagram - Concept on normalizationSatya Pal
The document discusses database normalization from the entity relationship diagram stage through fifth normal form. It describes how entities from the ER diagram become tables and how relationships are modeled. Anomalies in unnormalized relations are explained, along with how different normal forms address these issues. The document also discusses denormalization techniques used to improve query performance and some limitations of normalization.
Entity Relationship Diagrams (ERDs) are used to model relationships between entities in a database. The document discusses ERD components like entities, relationships, cardinality, and attributes. It provides an example of an ERD for a company with departments, supervisors, employees, and projects. Key entities are identified and their relationships and attributes are represented in the example ERD diagrams.
The document provides an overview of entity relationship diagrams (ERDs) including their basic components, different notations, and how to implement various relationship types in a relational database. ERDs depict entities, attributes, and relationships in a conceptual database design. Key points covered include the three main notations of ERDs, solving multi-valued attributes and many-to-many relationships, and how to implement one-to-one, one-to-many, and many-to-many relationships through primary and foreign key constraints.
The document discusses the entity-relationship (E-R) data model. It defines key concepts in E-R modeling including entities, attributes, entity sets, relationships, and relationship sets. It describes different types of attributes and relationships. It also explains how to represent E-R diagrams visually using symbols like rectangles, diamonds, and lines to depict entities, relationships, keys, and cardinalities. Primary keys, foreign keys, and weak entities are also covered.
The document discusses software design concepts and the Unified Modeling Language (UML). It introduces software design as translating requirements into a blueprint for constructing software. Key concepts discussed include abstraction, architecture, patterns, modularity, information hiding, and refinement. The document also explains UML's use for visual modeling through diagrams like use case diagrams, class diagrams, and state machine diagrams. It describes how UML can be used across the software development lifecycle.
The document discusses entity relationship diagrams and database design. It defines key concepts such as entities, attributes, relationships and cardinalities. Entities can have single-valued or multi-valued attributes. Relationships connect entities and can be one-to-one, one-to-many, many-to-one, or many-to-many. Primary keys uniquely identify entities and foreign keys define relationships between entities. Together these elements form a conceptual model of entities and their relationships within a database.
The document provides an overview of entity-relationship (E-R) modeling concepts including:
- Entity sets represent collections of real-world entities that share common properties
- Relationship sets define associations between entity sets
- Attributes provide additional information about entities and relationships
- Keys uniquely identify entities and relationships
- Cardinalities constrain how entities can participate in relationships
- E-R diagrams visually depict entity sets, attributes, relationships and constraints.
The document discusses state modeling and state diagrams. It defines states as representations of intervals of time that describe an object's behavioral condition. Events trigger transitions between states. A state diagram uses a graph to represent an object's states and the transitions between them caused by events. It specifies the object's response to input events over time. The document provides examples of how to notationally represent states, transitions, events, and other elements in a state diagram.
The document provides information on entity relationship diagrams (ERDs), including the objectives, components, and steps to create an ERD. It defines key ERD concepts like entities, attributes, relationships, and cardinality. It describes the entity modeling process and discusses how to recognize entities, attributes, relationships, and cardinalities in a database. It outlines the general steps to create an ERD, including identifying entities, finding relationships between entities, drawing a rough ERD, defining primary keys, identifying attributes, mapping attributes to entities, and drawing a fully attributed ERD. Sample ERDs are provided to illustrate concepts like cardinality constraints.
The document discusses entity-relationship (E-R) modeling concepts used to design databases. It defines entity sets as collections of entities that share common properties and attributes. Relationship sets describe associations between entity sets. E-R diagrams graphically represent entity sets as rectangles, relationship sets as diamonds, and attributes as ellipses linked to the appropriate sets. The document also covers mapping cardinalities between entity sets, roles that clarify relationships, and cardinality constraints depicted in E-R diagrams. The goal of E-R modeling is to design an E-R schema to logically represent entities, attributes, and relationships in a database.
The document provides information about database management systems and the relational database model. It discusses data models, entity relationship modeling, relational databases, normalization of database tables, and relational database design. Key topics covered include the entity relationship model, E-R diagrams, relationship sets, attributes, keys, normalization forms, and designing normalized database tables.
The document discusses the process of conceptual database design using an Entity-Relationship (ER) model. It begins by outlining the main steps: 1) requirements collection and analysis, 2) creating a conceptual schema using a high-level data model, 3) logical design mapping the conceptual schema to a implementation data model, and 4) physical design specifying storage structures. It then provides an example database for a company, describing the key entities, attributes, and relationships between employees, departments, projects, and dependents. Finally, it introduces some basic concepts of ER modeling including entities, attributes, relationships, cardinalities, and weak entities.
The document provides an overview of key concepts in entity-relationship (E-R) modeling, including entity sets, relationship sets, attributes, keys, E-R diagram notation, and reducing an E-R schema to tables. Specifically, it discusses entity sets and how they are represented by attributes, relationship sets and cardinalities, keys, using E-R diagrams to depict model components and constraints, and how an E-R schema can be converted into a relational database design with tables.
This document discusses entity-relationship (ER) modeling concepts including entity sets, relationship sets, attributes, keys, ER diagrams, weak entity sets, specialization, and generalization. The key points covered are:
- Entity sets represent types of objects, relationship sets represent associations among entity sets.
- Attributes represent properties of entities and relationships. Keys uniquely identify entities.
- ER diagrams visually depict entity sets, relationship sets, attributes, and keys.
- Weak entity sets do not have their own primary key and depend on a related strong entity set.
- Specialization and generalization allow subtypes and supertypes of entities.
The document provides an overview of the entity-relationship model for database design. It discusses key concepts such as entities, attributes, relationships, and cardinality constraints. It also covers advanced topics like weak entities, generalization/specialization, and aggregation. The entity-relationship model involves representing real-world objects and associations between objects using a graphical diagram to design the database at a conceptual level.
The document discusses entity-relationship (ER) diagrams and database design. It defines key concepts in ER diagrams like entities, attributes, relationships and how they are represented. It explains how to start building an ER diagram by defining entities and relationships based on a narrative. Different types of relationships and how they are drawn are covered, along with cardinality, keys, and other symbols used in ER diagrams. The document provides an example of an ER diagram for a banking system and discusses how an ER diagram can be converted into a relational database with tables.
This document provides an overview of entity-relationship (ER) modeling concepts including entity sets, relationship sets, attributes, keys, ER diagrams, specialization, generalization, aggregation, and design issues. It defines core ER concepts like entities, relationships, and attributes. It describes how ER diagrams visually represent these concepts using symbols like rectangles for entities and diamonds for relationships. It also covers advanced topics such as weak entities, cardinalities, and converting non-binary relationships to binary form.
The document provides an overview of entity-relationship (ER) modeling concepts including:
- Entity sets represent collections of real-world objects or concepts that share common properties
- Relationship sets represent associations between entity sets
- ER diagrams use graphical symbols like rectangles, diamonds, and lines to represent entity sets, relationship sets, and attributes
- Mapping cardinalities define the number of entities in one set that can be associated with entities in another set through a relationship
- Keys uniquely identify entities and relationships and primary keys are selected from candidate keys
- The document discusses entity-relationship (E-R) modeling concepts including entity sets, relationship sets, attributes, keys, E-R diagrams, mapping cardinalities, and design issues when converting between binary and non-binary relationships.
- It provides examples of how to represent various relationship types like one-to-one, one-to-many, many-to-one, and many-to-many using E-R diagrams with lines and arrows to show cardinality constraints.
- Guidelines are given for choosing between entity sets vs attributes and relationship sets, and converting non-binary relationships to binary form while preserving semantics.
The document provides an overview of entity-relationship (ER) modeling concepts including:
- Entity sets and relationship sets which form the basic constructs of an ER model
- Attributes, keys, and cardinality constraints which provide further details on entities and relationships
- ER diagrams which visually depict the ER model through graphical symbols
- Additional ER modeling features such as weak entities, specialization, and aggregation
The document concludes by discussing how an ER schema can be reduced to tables to represent the data in a relational database.
The document discusses enhanced entity-relationship (EER) modeling concepts used to more completely represent requirements of complex database applications. It introduces subclasses/superclasses to represent subgroupings of entities, with subclasses inheriting attributes and relationships from superclasses. Specialization defines subclasses of a superclass based on distinguishing characteristics, while generalization combines entity sets with common features into a higher-level superclass. Constraints on specialization/generalization include predicate-defined subclasses with membership conditions and attribute-defined specializations based on a defining attribute.
The document discusses enhanced entity-relationship (EER) modeling concepts used to more completely represent requirements of complex database applications. It introduces subclasses/superclasses to represent subgroupings of entities, with subclasses inheriting attributes and relationships from superclasses. Specialization defines subclasses of a superclass based on distinguishing characteristics, while generalization combines entity sets with common features into a higher-level superclass. Constraints on specialization/generalization include predicate-defined subclasses with membership conditions and attribute-defined specializations.
The document discusses database design concepts including entity sets, relationship sets, attributes, keys, and modeling techniques. It provides examples of how to represent various database design concepts in an entity-relationship (E-R) diagram including entities, relationships, cardinalities, participation constraints, weak entity sets, and translating n-ary relationships to binary relationships. Design choices such as using entity sets vs. attributes and relationship sets are also covered.
This document provides an overview of entity-relationship (E-R) modeling concepts for database design. It defines key E-R modeling elements including entity sets, relationship sets, attributes, keys, and cardinality constraints. It also covers E-R diagram notation and more advanced concepts such as weak entity sets, generalization/specialization, and aggregation. The goal of E-R modeling is to represent the structure and semantics of an organization's data to facilitate database design.
The document discusses the entity-relationship (E-R) model for conceptual database design. It describes key components of the E-R model including entity sets, relationship sets, attributes, keys, and E-R diagrams. It covers topics such as entity types, mapping cardinalities between entity sets, weak entity sets, and specialization and generalization for developing E-R schemas. The overall purpose is to introduce the basic concepts and notations of the E-R model for conceptual database design and modeling.
The document discusses the entity-relationship (E-R) model for conceptual database design. It describes how a database can be modeled as a collection of entities and relationships between entities. Entity sets contain entities of the same type, and relationship sets define associations among entity sets. The document outlines key E-R modeling concepts such as attributes, keys, cardinalities, participation constraints, and weak entities. It also discusses how to represent an E-R design using an E-R diagram.
The document provides an overview of the entity-relationship model, which is used to model databases. It discusses key concepts such as entity sets, relationship sets, attributes, keys, E-R diagrams, and how to map an E-R schema to tables. The entity-relationship model allows graphical representation of the relationships between entities in a database.
The document discusses the entity-relationship (E-R) model for conceptual database design. It describes key components of the E-R model including entity sets, relationship sets, attributes, keys, and E-R diagrams. Entity sets represent types of objects, relationship sets define associations among entity sets, and attributes provide additional information about entities and relationships. The document provides examples of how to model various cardinality constraints and participation constraints in E-R diagrams. It also covers advanced E-R features such as weak entity sets, specialization, and handling non-binary relationships.
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At Techbox Square, in Singapore, we're not just creative web designers and developers, we're the driving force behind your brand identity. Contact us today.
Structural Design Process: Step-by-Step Guide for BuildingsChandresh Chudasama
The structural design process is explained: Follow our step-by-step guide to understand building design intricacies and ensure structural integrity. Learn how to build wonderful buildings with the help of our detailed information. Learn how to create structures with durability and reliability and also gain insights on ways of managing structures.
At Techbox Square, in Singapore, we're not just creative web designers and developers, we're the driving force behind your brand identity. Contact us today.
Best practices for project execution and deliveryCLIVE MINCHIN
A select set of project management best practices to keep your project on-track, on-cost and aligned to scope. Many firms have don't have the necessary skills, diligence, methods and oversight of their projects; this leads to slippage, higher costs and longer timeframes. Often firms have a history of projects that simply failed to move the needle. These best practices will help your firm avoid these pitfalls but they require fortitude to apply.
Industrial Tech SW: Category Renewal and CreationChristian Dahlen
Every industrial revolution has created a new set of categories and a new set of players.
Multiple new technologies have emerged, but Samsara and C3.ai are only two companies which have gone public so far.
Manufacturing startups constitute the largest pipeline share of unicorns and IPO candidates in the SF Bay Area, and software startups dominate in Germany.
Brian Fitzsimmons on the Business Strategy and Content Flywheel of Barstool S...Neil Horowitz
On episode 272 of the Digital and Social Media Sports Podcast, Neil chatted with Brian Fitzsimmons, Director of Licensing and Business Development for Barstool Sports.
What follows is a collection of snippets from the podcast. To hear the full interview and more, check out the podcast on all podcast platforms and at www.dsmsports.net
[To download this presentation, visit:
https://www.oeconsulting.com.sg/training-presentations]
This presentation is a curated compilation of PowerPoint diagrams and templates designed to illustrate 20 different digital transformation frameworks and models. These frameworks are based on recent industry trends and best practices, ensuring that the content remains relevant and up-to-date.
Key highlights include Microsoft's Digital Transformation Framework, which focuses on driving innovation and efficiency, and McKinsey's Ten Guiding Principles, which provide strategic insights for successful digital transformation. Additionally, Forrester's framework emphasizes enhancing customer experiences and modernizing IT infrastructure, while IDC's MaturityScape helps assess and develop organizational digital maturity. MIT's framework explores cutting-edge strategies for achieving digital success.
These materials are perfect for enhancing your business or classroom presentations, offering visual aids to supplement your insights. Please note that while comprehensive, these slides are intended as supplementary resources and may not be complete for standalone instructional purposes.
Frameworks/Models included:
Microsoft’s Digital Transformation Framework
McKinsey’s Ten Guiding Principles of Digital Transformation
Forrester’s Digital Transformation Framework
IDC’s Digital Transformation MaturityScape
MIT’s Digital Transformation Framework
Gartner’s Digital Transformation Framework
Accenture’s Digital Strategy & Enterprise Frameworks
Deloitte’s Digital Industrial Transformation Framework
Capgemini’s Digital Transformation Framework
PwC’s Digital Transformation Framework
Cisco’s Digital Transformation Framework
Cognizant’s Digital Transformation Framework
DXC Technology’s Digital Transformation Framework
The BCG Strategy Palette
McKinsey’s Digital Transformation Framework
Digital Transformation Compass
Four Levels of Digital Maturity
Design Thinking Framework
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1. Chapter 2: Entity-Relationship
Model
Entity Sets
Relationship Sets
Design Issues
Mapping Constraints
Keys
E-R Diagram
Extended E-R Features
Design of an E-R Database Schema
Reduction of an E-R Schema to Tables
DBMS Notes by Ankur Shukla 2.1 www.ankurshukla.com
2. Entity Sets
A database can be modeled as:
a collection of entities,
relationship among entities.
An entity is an object that exists and is distinguishable from other
objects.
Example: specific person, company, event, plant
Entities have attributes
Example: people have names and addresses
An entity set is a set of entities of the same type that share the
same properties.
Example: set of all persons, companies, trees, holidays
DBMS Notes by Ankur Shukla 2.2 www.ankurshukla.com
3. Entity Sets customer and loan
customer-id customer- customer- customer- loan- amount
name street city number
DBMS Notes by Ankur Shukla 2.3 www.ankurshukla.com
4. Attributes
An entity is represented by a set of attributes, that is descriptive
properties possessed by all members of an entity set.
Example:
customer = (customer-id, customer-name,
customer-street, customer-city)
loan = (loan-number, amount)
Domain – the set of permitted values for each attribute
Attribute types:
Simple and composite attributes.
Single-valued and multi-valued attributes
E.g. multivalued attribute: phone-numbers
Derived attributes
Can be computed from other attributes
E.g. age, given date of birth
DBMS Notes by Ankur Shukla 2.4 www.ankurshukla.com
6. Relationship Sets
A relationship is an association among several entities
Example:
Hayes depositor A-102
customer entity relationship set account entity
A relationship set is a mathematical relation among n ≥ 2 entities,
each taken from entity sets
{(e1, e2, … en) | e1 ∈ E1, e2 ∈ E2, …, en ∈ En}
where (e1, e2, …, en) is a relationship
Example:
(Hayes, A-102) ∈ depositor
DBMS Notes by Ankur Shukla 2.6 www.ankurshukla.com
8. Relationship Sets (Cont.)
An attribute can also be property of a relationship set.
For instance, the depositor relationship set between entity sets
customer and account may have the attribute access-date
DBMS Notes by Ankur Shukla 2.8 www.ankurshukla.com
9. Degree of a Relationship Set
Refers to number of entity sets that participate in a relationship
set.
Relationship sets that involve two entity sets are binary (or degree
two). Generally, most relationship sets in a database system are
binary.
Relationship sets may involve more than two entity sets.
E.g. Suppose employees of a bank may have jobs
(responsibilities) at multiple branches, with different jobs at
different branches. Then there is a ternary relationship set
between entity sets employee, job and branch
Relationships between more than two entity sets are rare. Most
relationships are binary. (More on this later.)
DBMS Notes by Ankur Shukla 2.9 www.ankurshukla.com
10. Mapping Cardinalities
Express the number of entities to which another entity can be
associated via a relationship set.
Most useful in describing binary relationship sets.
For a binary relationship set the mapping cardinality must be
one of the following types:
One to one
One to many
Many to one
Many to many
DBMS Notes by Ankur Shukla 2.10 www.ankurshukla.com
11. Mapping Cardinalities
One to one One to many
Note: Some elements in A and B may not be mapped to any
elements in the other set
DBMS Notes by Ankur Shukla 2.11 www.ankurshukla.com
12. Mapping Cardinalities
Many to one Many to many
Note: Some elements in A and B may not be mapped to any
elements in the other set
DBMS Notes by Ankur Shukla 2.12 www.ankurshukla.com
13. Mapping Cardinalities affect ER Design
Can make access-date an attribute of account, instead of a
relationship attribute, if each account can have only one customer
I.e., the relationship from account to customer is many to one,
or equivalently, customer to account is one to many
DBMS Notes by Ankur Shukla 2.13 www.ankurshukla.com
14. E-R Diagrams
Rectangles represent entity sets.
Diamonds represent relationship sets.
Lines link attributes to entity sets and entity sets to relationship sets.
Ellipses represent attributes
Double ellipses represent multivalued attributes.
Dashed ellipses denote derived attributes.
Underline indicates primary key attributes (will study later)
DBMS Notes by Ankur Shukla 2.14 www.ankurshukla.com
15. E-R Diagram With Composite, Multivalued, and
Derived Attributes
DBMS Notes by Ankur Shukla 2.15 www.ankurshukla.com
17. Roles
Entity sets of a relationship need not be distinct
The labels “manager” and “worker” are called roles; they specify how
employee entities interact via the works-for relationship set.
Roles are indicated in E-R diagrams by labeling the lines that connect
diamonds to rectangles.
Role labels are optional, and are used to clarify semantics of the
relationship
DBMS Notes by Ankur Shukla 2.17 www.ankurshukla.com
18. Cardinality Constraints
We express cardinality constraints by drawing either a directed
line (→), signifying “one,” or an undirected line (—), signifying
“many,” between the relationship set and the entity set.
E.g.: One-to-one relationship:
A customer is associated with at most one loan via the relationship
borrower
A loan is associated with at most one customer via borrower
DBMS Notes by Ankur Shukla 2.18 www.ankurshukla.com
19. One-To-Many Relationship
In the one-to-many relationship a loan is associated with at most
one customer via borrower, a customer is associated with
several (including 0) loans via borrower
DBMS Notes by Ankur Shukla 2.19 www.ankurshukla.com
20. Many-To-One Relationships
In a many-to-one relationship a loan is associated with several
(including 0) customers via borrower, a customer is associated
with at most one loan via borrower
DBMS Notes by Ankur Shukla 2.20 www.ankurshukla.com
21. Many-To-Many Relationship
A customer is associated with several (possibly 0) loans
via borrower
A loan is associated with several (possibly 0) customers
via borrower
DBMS Notes by Ankur Shukla 2.21 www.ankurshukla.com
22. Participation of an Entity Set in a
Relationship Set
Total participation (indicated by double line): every entity in the entity
set participates in at least one relationship in the relationship set
E.g. participation of loan in borrower is total
every loan must have a customer associated to it via borrower
Partial participation: some entities may not participate in any
relationship in the relationship set
E.g. participation of customer in borrower is partial
DBMS Notes by Ankur Shukla 2.22 www.ankurshukla.com
23. Alternative Notation for Cardinality
Limits
Cardinality limits can also express participation constraints
DBMS Notes by Ankur Shukla 2.23 www.ankurshukla.com
24. Keys
A super key of an entity set is a set of one or more attributes
whose values uniquely determine each entity.
A candidate key of an entity set is a minimal super key
Customer-id is candidate key of customer
account-number is candidate key of account
Although several candidate keys may exist, one of the
candidate keys is selected to be the primary key.
DBMS Notes by Ankur Shukla 2.24 www.ankurshukla.com
25. Keys for Relationship Sets
The combination of primary keys of the participating entity sets
forms a super key of a relationship set.
(customer-id, account-number) is the super key of depositor
NOTE: this means a pair of entity sets can have at most one
relationship in a particular relationship set.
E.g. if we wish to track all access-dates to each account by each
customer, we cannot assume a relationship for each access. We
can use a multivalued attribute though
Must consider the mapping cardinality of the relationship set
when deciding the what are the candidate keys
Need to consider semantics of relationship set in selecting the
primary key in case of more than one candidate key
DBMS Notes by Ankur Shukla 2.25 www.ankurshukla.com
26. E-R Diagram with a Ternary
Relationship
DBMS Notes by Ankur Shukla 2.26 www.ankurshukla.com
27. Cardinality Constraints on Ternary
Relationship
We allow at most one arrow out of a ternary (or greater degree)
relationship to indicate a cardinality constraint
E.g. an arrow from works-on to job indicates each employee works
on at most one job at any branch.
If there is more than one arrow, there are two ways of defining the
meaning.
E.g a ternary relationship R between A, B and C with arrows to B and C
could mean
1. each A entity is associated with a unique entity from B and C or
2. each pair of entities from (A, B) is associated with a unique C entity,
and each pair (A, C) is associated with a unique B
Each alternative has been used in different formalisms
To avoid confusion we outlaw more than one arrow
DBMS Notes by Ankur Shukla 2.27 www.ankurshukla.com
28. Binary Vs. Non-Binary Relationships
Some relationships that appear to be non-binary may be better
represented using binary relationships
E.g. A ternary relationship parents, relating a child to his/her father and
mother, is best replaced by two binary relationships, father and mother
Using two binary relationships allows partial information (e.g. only
mother being know)
But there are some relationships that are naturally non-binary
E.g. works-on
DBMS Notes by Ankur Shukla 2.28 www.ankurshukla.com
29. Converting Non-Binary Relationships to
Binary Form
In general, any non-binary relationship can be represented using binary
relationships by creating an artificial entity set.
Replace R between entity sets A, B and C by an entity set E, and three
relationship sets:
1. RA, relating E and A 2.RB, relating E and B
3. RC, relating E and C
Create a special identifying attribute for E
Add any attributes of R to E
For each relationship (ai , bi , ci) in R, create
1. a new entity ei in the entity set E 2. add (ei , ai ) to RA
3. add (ei , bi ) to RB 4. add (ei , ci ) to RC
DBMS Notes by Ankur Shukla 2.29 www.ankurshukla.com
30. Converting Non-Binary Relationships
(Cont.)
Also need to translate constraints
Translating all constraints may not be possible
There may be instances in the translated schema that
cannot correspond to any instance of R
Exercise: add constraints to the relationships RA, RB and RC to
ensure that a newly created entity corresponds to exactly one entity
in each of entity sets A, B and C
We can avoid creating an identifying attribute by making E a weak
entity set (described shortly) identified by the three relationship sets
DBMS Notes by Ankur Shukla 2.30 www.ankurshukla.com
31. Design Issues
Use of entity sets vs. attributes
Choice mainly depends on the structure of the enterprise being
modeled, and on the semantics associated with the attribute in
question.
Use of entity sets vs. relationship sets
Possible guideline is to designate a relationship set to describe an
action that occurs between entities
Binary versus n-ary relationship sets
Although it is possible to replace any nonbinary (n-ary, for n > 2)
relationship set by a number of distinct binary relationship sets, a n-
ary relationship set shows more clearly that several entities
participate in a single relationship.
Placement of relationship attributes
DBMS Notes by Ankur Shukla 2.31 www.ankurshukla.com
32. How about doing an ER design
interactively on the board?
Suggest an application to be
modeled.
33. Weak Entity Sets
An entity set that does not have a primary key is referred to as a
weak entity set.
The existence of a weak entity set depends on the existence of a
identifying entity set
it must relate to the identifying entity set via a total, one-to-many
relationship set from the identifying to the weak entity set
Identifying relationship depicted using a double diamond
The discriminator (or partial key) of a weak entity set is the set of
attributes that distinguishes among all the entities of a weak
entity set.
The primary key of a weak entity set is formed by the primary key
of the strong entity set on which the weak entity set is existence
dependent, plus the weak entity set’s discriminator.
DBMS Notes by Ankur Shukla 2.33 www.ankurshukla.com
34. Weak Entity Sets (Cont.)
We depict a weak entity set by double rectangles.
We underline the discriminator of a weak entity set with a
dashed line.
payment-number – discriminator of the payment entity set
Primary key for payment – (loan-number, payment-number)
DBMS Notes by Ankur Shukla 2.34 www.ankurshukla.com
35. Weak Entity Sets (Cont.)
Note: the primary key of the strong entity set is not explicitly
stored with the weak entity set, since it is implicit in the
identifying relationship.
If loan-number were explicitly stored, payment could be made a
strong entity, but then the relationship between payment and
loan would be duplicated by an implicit relationship defined by
the attribute loan-number common to payment and loan
DBMS Notes by Ankur Shukla 2.35 www.ankurshukla.com
36. More Weak Entity Set Examples
In a university, a course is a strong entity and a course-offering
can be modeled as a weak entity
The discriminator of course-offering would be semester (including
year) and section-number (if there is more than one section)
If we model course-offering as a strong entity we would model
course-number as an attribute.
Then the relationship with course would be implicit in the course-
number attribute
DBMS Notes by Ankur Shukla 2.36 www.ankurshukla.com
37. Specialization
Top-down design process; we designate subgroupings within an
entity set that are distinctive from other entities in the set.
These subgroupings become lower-level entity sets that have
attributes or participate in relationships that do not apply to the
higher-level entity set.
Depicted by a triangle component labeled ISA (E.g. customer “is
a” person).
Attribute inheritance – a lower-level entity set inherits all the
attributes and relationship participation of the higher-level entity
set to which it is linked.
DBMS Notes by Ankur Shukla 2.37 www.ankurshukla.com
39. Generalization
A bottom-up design process – combine a number of entity sets
that share the same features into a higher-level entity set.
Specialization and generalization are simple inversions of each
other; they are represented in an E-R diagram in the same way.
The terms specialization and generalization are used
interchangeably.
DBMS Notes by Ankur Shukla 2.39 www.ankurshukla.com
40. Specialization and Generalization
(Contd.)
Can have multiple specializations of an entity set based on
different features.
E.g. permanent-employee vs. temporary-employee, in addition to
officer vs. secretary vs. teller
Each particular employee would be
a member of one of permanent-employee or temporary-employee,
and also a member of one of officer, secretary, or teller
The ISA relationship also referred to as superclass - subclass
relationship
DBMS Notes by Ankur Shukla 2.40 www.ankurshukla.com
41. Design Constraints on a
Specialization/Generalization
Constraint on which entities can be members of a given
lower-level entity set.
condition-defined
E.g. all customers over 65 years are members of senior-
citizen entity set; senior-citizen ISA person.
user-defined
Constraint on whether or not entities may belong to more than
one lower-level entity set within a single generalization.
Disjoint
an entity can belong to only one lower-level entity set
Noted in E-R diagram by writing disjoint next to the ISA
triangle
Overlapping
an entity can belong to more than one lower-level entity set
DBMS Notes by Ankur Shukla 2.41 www.ankurshukla.com
42. Design Constraints on a
Specialization/Generalization
(Contd.)
Completeness constraint -- specifies whether or not an entity in
the higher-level entity set must belong to at least one of the
lower-level entity sets within a generalization.
total : an entity must belong to one of the lower-level entity sets
partial: an entity need not belong to one of the lower-level entity
sets
DBMS Notes by Ankur Shukla 2.42 www.ankurshukla.com
43. Aggregation
Consider the ternary relationship works-on, which we saw earlier
Suppose we want to record managers for tasks performed by an
employee at a branch
DBMS Notes by Ankur Shukla 2.43 www.ankurshukla.com
44. Aggregation (Cont.)
Relationship sets works-on and manages represent overlapping
information
Every manages relationship corresponds to a works-on relationship
However, some works-on relationships may not correspond to any
manages relationships
So we can’t discard the works-on relationship
Eliminate this redundancy via aggregation
Treat relationship as an abstract entity
Allows relationships between relationships
Abstraction of relationship into new entity
Without introducing redundancy, the following diagram represents:
An employee works on a particular job at a particular branch
An employee, branch, job combination may have an associated manager
DBMS Notes by Ankur Shukla 2.44 www.ankurshukla.com
45. E-R Diagram With Aggregation
DBMS Notes by Ankur Shukla 2.45 www.ankurshukla.com
46. E-R Design Decisions
The use of an attribute or entity set to represent an object.
Whether a real-world concept is best expressed by an entity set
or a relationship set.
The use of a ternary relationship versus a pair of binary
relationships.
The use of a strong or weak entity set.
The use of specialization/generalization – contributes to
modularity in the design.
The use of aggregation – can treat the aggregate entity set as a
single unit without concern for the details of its internal structure.
DBMS Notes by Ankur Shukla 2.46 www.ankurshukla.com
47. E-R Diagram for a Banking
Enterprise
DBMS Notes by Ankur Shukla 2.47 www.ankurshukla.com
48. How about doing another ER
design interactively on the board?
49. Summary of Symbols Used in E-R
Notation
DBMS Notes by Ankur Shukla 2.49 www.ankurshukla.com
50. Summary of Symbols (Cont.)
DBMS Notes by Ankur Shukla 2.50 www.ankurshukla.com
52. UML
UML: Unified Modeling Language
UML has many components to graphically model different
aspects of an entire software system
UML Class Diagrams correspond to E-R Diagram, but several
differences.
DBMS Notes by Ankur Shukla 2.52 www.ankurshukla.com
53. Summary of UML Class Diagram Notation
DBMS Notes by Ankur Shukla 2.53 www.ankurshukla.com
54. UML Class Diagrams (Contd.)
Entity sets are shown as boxes, and attributes are shown within the
box, rather than as separate ellipses in E-R diagrams.
Binary relationship sets are represented in UML by just drawing a
line connecting the entity sets. The relationship set name is written
adjacent to the line.
The role played by an entity set in a relationship set may also be
specified by writing the role name on the line, adjacent to the entity
set.
The relationship set name may alternatively be written in a box,
along with attributes of the relationship set, and the box is
connected, using a dotted line, to the line depicting the relationship
set.
Non-binary relationships drawn using diamonds, just as in ER
diagrams
DBMS Notes by Ankur Shukla 2.54 www.ankurshukla.com
55. UML Class Diagram Notation (Cont.)
overlapping
disjoint
*Note reversal of position in cardinality constraint depiction
*Generalization can use merged or separate arrows independent
of disjoint/overlapping
DBMS Notes by Ankur Shukla 2.55 www.ankurshukla.com
56. UML Class Diagrams (Contd.)
Cardinality constraints are specified in the form l..h, where l denotes
the minimum and h the maximum number of relationships an entity
can participate in.
Beware: the positioning of the constraints is exactly the reverse of the
positioning of constraints in E-R diagrams.
The constraint 0..* on the E2 side and 0..1 on the E1 side means that
each E2 entity can participate in at most one relationship, whereas
each E1 entity can participate in many relationships; in other words,
the relationship is many to one from E2 to E1.
Single values, such as 1 or * may be written on edges; The single
value 1 on an edge is treated as equivalent to 1..1, while * is
equivalent to 0..*.
DBMS Notes by Ankur Shukla 2.56 www.ankurshukla.com
57. Reduction of an E-R Schema to
Tables
Primary keys allow entity sets and relationship sets to be
expressed uniformly as tables which represent the
contents of the database.
A database which conforms to an E-R diagram can be
represented by a collection of tables.
For each entity set and relationship set there is a unique
table which is assigned the name of the corresponding
entity set or relationship set.
Each table has a number of columns (generally
corresponding to attributes), which have unique names.
Converting an E-R diagram to a table format is the basis
for deriving a relational database design from an E-R
diagram.
DBMS Notes by Ankur Shukla 2.57 www.ankurshukla.com
58. Representing Entity Sets as Tables
A strong entity set reduces to a table with the same attributes.
DBMS Notes by Ankur Shukla 2.58 www.ankurshukla.com
59. Composite and Multivalued
Attributes
Composite attributes are flattened out by creating a separate attribute
for each component attribute
E.g. given entity set customer with composite attribute name with
component attributes first-name and last-name the table corresponding
to the entity set has two attributes
name.first-name and name.last-name
A multivalued attribute M of an entity E is represented by a separate
table EM
Table EM has attributes corresponding to the primary key of E and an
attribute corresponding to multivalued attribute M
E.g. Multivalued attribute dependent-names of employee is represented
by a table
employee-dependent-names( employee-id, dname)
Each value of the multivalued attribute maps to a separate row of the
table EM
E.g., an employee entity with primary key John and
dependents Johnson and Johndotir maps to two rows:
(John, Johnson) and (John, Johndotir)
DBMS Notes by Ankur Shukla 2.59 www.ankurshukla.com
60. Representing Weak Entity Sets
A weak entity set becomes a table that includes a column for
the primary key of the identifying strong entity set
DBMS Notes by Ankur Shukla 2.60 www.ankurshukla.com
61. Representing Relationship Sets
as Tables
A many-to-many relationship set is represented as a table with
columns for the primary keys of the two participating entity sets,
and any descriptive attributes of the relationship set.
E.g.: table for relationship set borrower
DBMS Notes by Ankur Shukla 2.61 www.ankurshukla.com
62. Redundancy of Tables
Many-to-one and one-to-many relationship sets that are total
on the many-side can be represented by adding an extra
attribute to the many side, containing the primary key of the
one side
E.g.: Instead of creating a table for relationship account-
branch, add an attribute branch to the entity set account
DBMS Notes by Ankur Shukla 2.62 www.ankurshukla.com
63. Redundancy of Tables (Cont.)
For one-to-one relationship sets, either side can be chosen to act
as the “many” side
That is, extra attribute can be added to either of the tables
corresponding to the two entity sets
If participation is partial on the many side, replacing a table by an
extra attribute in the relation corresponding to the “many” side
could result in null values
The table corresponding to a relationship set linking a weak
entity set to its identifying strong entity set is redundant.
E.g. The payment table already contains the information that would
appear in the loan-payment table (i.e., the columns loan-number and
payment-number).
DBMS Notes by Ankur Shukla 2.63 www.ankurshukla.com
64. Representing Specialization as
Tables
Method 1:
Form a table for the higher level entity
Form a table for each lower level entity set, include primary key of
higher level entity set and local attributes
table table attributes
person name, street, city
customer name, credit-rating
employee name, salary
Drawback: getting information about, e.g., employee requires
accessing two tables
DBMS Notes by Ankur Shukla 2.64 www.ankurshukla.com
65. Representing Specialization as
Tables (Cont.)
Method 2:
Form a table for each entity set with all local and inherited
attributes
table table attributes
person name, street, city
customer name, street, city, credit-rating
employee name, street, city, salary
If specialization is total, table for generalized entity (person) not
required to store information
Can be defined as a “view” relation containing union of
specialization tables
But explicit table may still be needed for foreign key constraints
Drawback: street and city may be stored redundantly for persons
who are both customers and employees
DBMS Notes by Ankur Shukla 2.65 www.ankurshukla.com
66. Relations Corresponding to
Aggregation
To represent aggregation, create a table containing
primary key of the aggregated relationship,
the primary key of the associated entity set
Any descriptive attributes
DBMS Notes by Ankur Shukla 2.66 www.ankurshukla.com
67. Relations Corresponding to
Aggregation (Cont.)
E.g. to represent aggregation manages between relationship
works-on and entity set manager, create a table
manages(employee-id, branch-name, title, manager-name)
Table works-on is redundant provided we are willing to store
null values for attribute manager-name in table manages
DBMS Notes by Ankur Shukla 2.67 www.ankurshukla.com
69. E-R Diagram for Exercise 2.10
DBMS Notes by Ankur Shukla 2.69 www.ankurshukla.com
70. E-R Diagram for Exercise 2.15
DBMS Notes by Ankur Shukla 2.70 www.ankurshukla.com
71. E-R Diagram for Exercise 2.22
DBMS Notes by Ankur Shukla 2.71 www.ankurshukla.com
72. E-R Diagram for Exercise 2.15
DBMS Notes by Ankur Shukla 2.72 www.ankurshukla.com
73. Existence Dependencies
If the existence of entity x depends on the existence of
entity y, then x is said to be existence dependent on y.
y is a dominant entity (in example below, loan)
x is a subordinate entity (in example below, payment)
loan loan-payment payment
If a loan entity is deleted, then all its associated payment entities
must be deleted also.
DBMS Notes by Ankur Shukla 2.73 www.ankurshukla.com