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Construct a clean and concise ER diagram for the NHL database using the Chen notation as in your textbook. List your assumptions and clearly indicate the cardinality mappings as well as any role indicators in your ER diagram. Here is one sample solution. Note that other diagrams are possible depending on assumptions. date score game host guest ...
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Below we present several entity relationship diagrams for modeling information about authors, editors and books. Note that aid is the key of Authors, eid is the key of Editors and bid is the key of Books. For each of the entity relationship diagrams below: (a) State briefly the meaning of the diagram. Emphasize the constraints in the diagrams.
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- Lecture 7
- Comprehensive
- Concise/High-level
- Algorithmically Transformable
- Set of entities that have the same attributes
- CAR
- DEPARTMENT
- PROJECT
- DEPT
- FACULTY
- STUDENT
- DEPT
- STUDENT
- DEPT
- is important)
- Tutee
- >N, can go to (1) entity
Context Design & Implementation Process Goals of Conceptual Design Entity-Relationship (ER) Model One ER Diagrammatic Notation Requirements Elicitation Approaches to Conceptual Design
Entity types, relationships, and constraints Sanity check of data & functional requirements Reference for [unit/integration] testing/analysis
Easy to understand technically Easy to communicate with non-technical users Facilitates focus on data (vs. storage/implementation details)
• Improves application development efficiency, reduces errors Entity • Thing in the real world Attribute Property of an entity Most of what we store in the database Relationship Association between sets of entities Possibly with attribute(s) Graphical depiction of an ER model Many notations, this class... All cars have a year, age, make, model, reg...
Make Year Model All cars have a year, make, and model.
Can be subdivided into smaller subparts All cars have a year, make, model, and registration. Can take a [possibly specified] number of values. All cars have a year, make, model, registration, and some number of colors. Make Year Model Color CAR Registration State Number The value uniquely identifies each entity All cars have a year, make, model, re...
Manager Manager_ Start_Date Draw an ERD for the following description: A department controls a number of projects, each of which has a unique name, a unique number, and a single location. Location Name Number
Controlling_ Department Draw an ERD for the following description: We store each employee’s name (first, last, MI), Social Security number (SSN), street address, salary, sex (gender), and birth date. An employee is assigned to one department, but may work on several projects, which are not necessarily controlled by the same department. We keep trac...
CHAIR_F All departments have a faculty member who serves as the chair. A faculty member can only chair one
department. Associates one or more sets of entities
All students must have a department in which they major.
CHAIR_F FACULTY Associates one or more sets of entities
MINOR_D Students may have any number of departments in which they minor.
CHAIR_F FACULTY Associates one or more sets of entities – One = recursive (role
MAJOR_D Constrains the number of entities that can participate in each role of the relationship Tutor
All departments have a faculty member who serves as the chair. A faculty member can only chair one department. Constrains the number of entities that can participate in each role of the relationship Constrains the number of entities that can participate in each role of the relationship Constrains the number of entities that can participate in each ...
N MAJOR_D STUDENT N MINOR_D Tutor N Tutee M TUTORS Each department chair has an office. Office
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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 su-perkey. Answer: A superkey is a set of one or more attributes that, taken collectively, al-lows us to identify uniquely an entity in the entity set. A superkey may contain extraneous attributes.
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Entity-Relationship (ER) model. Popular high-level conceptual data model. ER diagrams. Diagrammatic notation associated with the ER model. STEPS IN DATABASE DESIGN. Requirements collection and analysis. DB designers interview prospective DB users to understand and document data requirements. Data requirements.
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The ER diagram/relational database schema contains several instances of data redundancy. Please identify one instance where a data redundancy issue exists. ( 3 pts ).
Exercise 1 — E/R modeling. Objective: to practice E/R modeling. 1. A calendar program that allows users to browse each other’s calendars and to book common appointments shall be developed. The program has a database which keeps track of the users and their calendars. You use the calendar to store data concerning appointments.
