Design -The entity relation design without regard to what RDBMS or system it will be on. 2. Physical Design-The design adapted to the RDBMS and system constraints and features. 3. Naming Convention – A set of rules or suggestions that promote consistency in the naming of database objects. 4. ERDs- (Entity Relation Diagram) One common method of depicting entities and relations in a diagram. 5. Crow’s Feet Notation - crow’s feet notation actually conveys more information about a relationship than the
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Also called an entity-relationship (ER) diagram‚ 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. A relationship is how the data is shared between entities. There are three types of relationships between entities: 1. One-to-One One instance of an entity (A) is associated with one other
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The Entity-Relationship Model ------------------------------------------------- Top of Form Bottom of Form Database Design Goal of design is to generate a formal specification of the database schema Methodology: 1. Use E-R model to get a high-level graphical view of essential components of enterprise and how they are related 2. Then convert E-R diagram to SQL DDL‚ or whatever database model you are using E-R Model is not SQL based. It ’s not limited to any particular DBMS. It is a
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Review Entity-Relationship Diagrams and the Relational Model CS 186‚ Fall 2007‚ Lecture 2 R & G‚ Chaps. 2&3 A relationship‚ I think‚ is like a shark‚ you know? It has to constantly move forward or it dies. And I think what we got on our hands is a dead shark. Woody Allen (from Annie Hall‚ 1979) • Why use a DBMS? OS provides RAM and disk Review • Why use a DBMS? OS provides RAM and disk – Concurrency – Recovery – Abstraction‚ Data Independence – Query Languages – Efficiency (for most tasks)
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purchase of the merchandise. 1. ER model Figure 1 shows the ER mode of this database project. Its entities includes the product (merchandise‚ includes laptop and desktop subclass)‚ manufacturer‚ warehouse‚ store and customer. It also has the manufacturer-make‚ product-in-store‚ product-in-warehouse‚ and customer-order relationships. 1.1 Entities. This project focuses on the product (or merchandise) entity. Its attributes include item number‚ model‚ type‚ price and quantity. The item number
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Database Models s L11: ER Diagrams Kieran Herley Summary The database design process and the role of ER modelling in same. Basic constituents of ER diagrams: entities‚ relationships and attributes. While designing database it’s handy to have notation to “sketch” schema s Two common diagrammatic notations: x x s UML diagrams (Universal Modelling Language) ER diagrams (Entity Relationship) → cs1106 choice Captures the information requirements of our database: what data it con and how
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CHAPTER 2 Methodology The Research Design The descriptive method of research was used for this study. To define the descriptive type of research‚ Creswell (1994) stated that the descriptive method of research is to gather information about the present existing condition. The emphasis is on describing rather than on judging or interpreting. The aim of descriptive research is to verify formulated hypotheses that refer to the present situation in order to elucidate it. The descriptive
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the naming conventions because it’s clear concise and easy to read. Entity Relation Diagram structures and notations are different at least five features. Some allow attributes in a relationship‚ how they represent cardinality and participation constraints‚ the place where they specify constraints‚ or they portray overlapping and split subclass entity-types‚ or they show total or partial narrowing down‚ and whether they model the foreign key at the ERD level. Bachman Notation also known as data
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Hospital want to use entity-relationship modeling to understand its data requirements? What other ways might the hospital want to model its information requirements? This hospital wants to use E-R modeling to understand data requirements. E-R modeling is very easy to understand and shows all the business rules. • Entity-relationship modeling is logical representation of the data for an organization or for a business area. The E-R model is expressed in terms of entities in the business environment
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Exercises 9 address driver-id person name owns license model year car report-number location date driver participated accident damage-amount Figure 2.1 E-R diagram for a Car-insurance company. Exercises 2.1 Explain the distinctions among the terms primary key‚ candidate key‚ and superkey. Answer: A superkey is a set of one or more attributes that‚ taken collectively‚ allows us to identify uniquely an entity in the entity set. A superkey may contain extraneous attributes. If K
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