Entity Relationship Diagrams - 747 Words

An entity relationship diagram is the basic design model for any database. It is the major deliverable for a conceptual database design. It is the logical organization of any data in the database and is usually made up of three components namely; entities, attributes and relationships. Entities are the major categories of data in the database and are usually represented by rectangles. Attributes are the characteristics of the entities and are usually written in the rectangle. Relationships are the connections between entities and are usually represented using lines joining the rectangles. Entities that share major characteristics are known as entity types, and are also referred to as classes. An entity instance is the individual occurrence of one entity type. It is important to define entity types as it makes it easier to determine the requirements of the database and how it will be structured. In defining an attribute, the analyst must state the importance of the attribute, the value of the attribute and whether the value of this attribute can change. When drawing an entity relationship diagram, the analyst must be aware of the following types of attributes; multi-valued attributes, required attributes, optional attributes, composite attributes and derived attributes. When showing relationships, an analyst must be aware of three types of relationships; unary (between instances of one entity type), binary (between instances of two entity types), and ternary (betweenShow MoreRelatedEntity Relationship Diagram1225 Words   |  5 PagesEntity Relationship Diagram The bellow diagram is what is refered to as an Entity Relationship Diagram. Its purpose is to show the relationship between different data in the hotel management program , and the actions that are performed on it. And how data from different objects relate to each other. Legend The Data Entities represent data that will need to be stored on the system, in general terms. The Relationships represent actions that will occur to the Data Entities, or Weak Entities. Read MoreEntity-Relationship Diagrams and the Relational Model2499 Words   |  10 PagesReview Entity-Relationship Diagrams and the Relational Model CS 186, Fall 2007, Lecture 2 R G, Chaps. 23 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)Read MoreEntity-relationship Model and E-r Diagram2109 Words   |  9 Pagesmodel 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 is a superkey, then so is any superset of K. A superkey forRead MoreData Modeling Using Entity Relationship Diagrams : A Step Wise Method1798 Words   |  8 Pages Best Practice: ERDs â€Å"Data Modeling Using Entity Relationship Diagrams: A Step-Wise Method† IST 659 - Syracuse University September 30, 2014 Jared S. Mandel â€Æ' Introduction Databases are the center of many technology and non-technology focused businesses. They are used in retail, healthcare, education and government. Databases are essentially in entering, storing, managing and referencing data, and can be simple in nature, or extremely complex. In order for a database to be implementedRead MoreEntity Relationship Diagram of a Video Rental Store601 Words   |  2 PagesVideo Rental Store Entity Relationship Diagram For this video rental store, the movie database contains three kinds of records namely customers, tapes, and rentals. Whenever a customer visits the video store, the database is looked at to determine whether the store attendants already know the new customer; and if not, a new record is added to update the new customer’s details (Beynon-Davies, 2004). In the database, important information about the customer that is stored includes the customers nameRead MoreApplying Normalized Tables And The Model Of The Entity Relationship Diagram Can Then Improve The Conceptual Model1206 Words   |  5 Pagesattributes within the entity table to achieve its goal. Since the Entity Relationship Diagram will also contain the appropriations amongst the attributes, as a common base to identify the entity type structure, than it is possible to then apply the normalization principles, all during the conceptual data modeling phase. Enacting Normalization during the Entity Relationship Diagram can then improve the conceptual model, and therefore speed its utilization. The Entity Relationship Diagram has acquired lotsRead MoreEntity-relationship Model and Mountain View Community1374 Words   |  6 PagesHospital 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 environmentRead MoreHuffman Trucking Entity-Relationship Model1667 Words   |  7 PagesThe 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 aRead MoreBec Case Study Essay1624 Words   |  7 PagesSolutions 1. Review the data flow diagrams you developed for questions in the BEC case at the end of Chapter 5 (or diagrams given to you by your instructor.) Study the data flows and data stores on these diagrams and decide if you agree with the team’s conclusion that there are only the six entity types listed in this case and in BEC Figure 6-1. If you disagree, define additional entity types, explain why they are necessary, and modify BEC Figure 6-1. The six entity types in BEC Figure 1 are theRead MoreEvolution of Data Models1122 Words   |  5 Pagesrepresenting information using parent/child relationships: each parent can have many children, but each child has only parent. All attributes of a specific record are listed under an entity type. Example of a hierarchical model In a database an entity type is the equivalent of a table. Each individual record is represented as a row, and each attribute as a column. Entity types are related to each other using 1:N mappings, also known as one-to-many relationship. This model is recognized as the first