• Entity
    An entity set that does not possess sufficient attributes to form a primary key is called a weak entity set. One that does have a primary key is called a strong entity set. For example, The entity set transaction has attributes transaction-number, date and amount. Different transactions on different...
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  • Er Model
    Chapter 6: Entity-Relationship Model  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 Example: people have names and...
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  • Dbms
    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...
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  • Er Diagram
    ' • Keys Chapter 2: Entity-Relationship Model $ • Entity Sets • Relationship Sets • Design Issues • Mapping Constraints • E–R Diagram & • Extended E-R Features • Design of an E-R Database Schema • Reduction of an E-R Schema to Tables Database Systems Concepts 2.1 Silberschatz...
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  • Database Systems
    The entity-relationship model (or ER model) is a way of graphically representing the logical relationships of entities (or objects) in order to create a database. entity type is a collection of entity instances sharing similar properties Strong Entity Vs Weak Entity An entity set that does not have...
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  • Er Model
    com C H A P T E R 2 Entity Relationship Model This chapter introduces the entity-relationship model in detail. The chapter covers numerous features of the model, several of which can be omitted depending on the planned coverage of the course. Weak entity sets (Section 2.6), design constraints...
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  • Database Management System
    model into a set of relations – relational schema and 3) Normalizing the relations. Once ER / EER model has been developed for the application , ER/ EER diagram can be mapped into a relational model . ER/ EER diagram consists of the following components. 1) Entities (Strong , Weak) with attributes ...
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  • Huffman Trucking Entity-Relationship Model
    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...
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  • Hello
    McFadyen Relationship Types A Relationship Type defines a relationship set among entities of certain entity types A relationship type is illustrated in an ERD using a diamond symbol. Consider the following diagram that shows two entity types (Department and Instructor) and the concept (a relationship) that...
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  • Erd Model
    CHAPTER 11: ENTITY-RELATIONSHIP MODELLING What is it about? • ER model is used to show the Conceptual schema of an organisation. • Independent of specific data model or DBMS • The model is later transformed into a Logical model (e.g. relational) on which the physical database is built ...
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  • E-R Diagram
    Introduction:- In 1976 ,Chen developed the Entity-Relationship Diagrams ,a high-level data model that is useful in developing a conceptual design for database . An ER diagram is a diagram containing entities or “items”, relationships among them, and attributes of the entities . The E-R model is one of the best...
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  • Chapter 4 -SQL
    main components: Entity – as an object of interest to as the end user; it also represents a real-world object, the words entity and object are often used interchangeably. An entity actually refers to the entity set and not to a single entity occurrence. In other words, the word entity in the ERM corresponds...
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  • Database Management Intro
    RDBMS is a type of database management system (DBMS) that stores data in the form of related tables. While an ERDBMS handles the relationships between entities and the attributes. REQUIRED AND OPTIONAL ATTRIBUTE Required attributes are attributes which need values while the optional attributes are attributes...
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  • Databasemanagementsystems
    database :  A database is a collection of stored operational data used by various applications and/or users by some particular enterprise or by a set of outside authorized applications and authorized users. DataBase Management System :  A DataBase Management System (DBMS) is a software system that...
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  • world champ
    INSTRUCTOR entity as weak because of the presumed non-uniqueness of instructor names and the dependence on COURSE. If the instructor were identified uniquely with an attribute like instructor social security number, and if instructors could exist independent of course, then the entity could become...
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  • Document Management
    several limitations of traditional file processing systems that are * Separation and isolation of data * Each program maintains its own set of data. * Users of one program may be unaware of potentially useful data held by other programs. * Duplication of data * Same data...
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  • Entity Relational Diagram
    Entity-Relationship (E/R) Model Dr P Sreenivasa Kumar Professor CS&E Dept I I T Madras Entity-Relationship (E/R) Model Widely used conceptual level data model • proposed by Peter P Chen in 1970s Data model to describe the database system at the requirements collection stage • high level description...
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  • question answer
    12.8 Describe how strong and weak entity types differ and provide an example of each. A strong entity type is an entity type that is not existence-dependent on some other entity type A weak entity type is an entity type that is existence-dependent on some other entity type. ...
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  • Economics
    Objectives • • • • Define terms for the relational data model Brief introduction to SQL Transform E-R diagrams to relations Create tables with entity and relational integrity constraints 2 Steps in Database Problem Solving Study and Analyze w/Team Business Problem Interviews & Integrated...
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  • Site Recommendations
    Answer 1 a. Entity Type There are different types of entities in ER model. The existences of an entity depend on the existence of one or more other entities, and are called as existence dependent. Entities which are not dependent on other entities are called as not existence dependent. Following...
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