Entity Relationship Diagram Examples
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Choose your CountryEntity Relationship Diagram Research Paper - 1214 Words
Entity Relationship Diagram
Entity Relationship Diagram
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Entity 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. The Weak Entities represent data that does not exist, except in relation to a Data Entity.
Data Dictionary
Below is a data dictionary used to demostrate how data will be represented in the computer system, and how different modules are inter related.
Access Level = (Front Desk) + (Kitchen) + (Management)
* An access level which denotes exactly which areas, a user has access to.* Amount Paid= $ + INT + '.' + [00 | 01 | .. | 99]
The amount the customer has actually paid.
Arrival Date = Date
* Represents the date the cutomers arrived.*
Balance $ + INT + '.' + [00 | 01 | .. | 99]
The amount remaining for the customer to pay.
Bill to = Room Number
* A valid room number in the hotel to bill a some to.*
Bus. Phone = Phone Number
* Represents the bussiness phone number of the customer.*
Calendar Day = Date + {Room}
* Represnts all of the days on the calendar, along with which rooms are booked for that day.* Category = [Single | Double | Triple]
* A category represents the size of a room.*
City = STRING(64)
* Represents the name of a city.*
Country = STRING(64)
* Represents the name of a country.*
Cost of Phone Call= $ + INT + '.' + [00 | 01 | .. | 99]
* The cost of an outgoing phone call.*
Credit Card Number [00 0000 | 00 0001 | .... .... .... .... | 99 9999] * Represents a credit card number.*
Customer Info = Guest Name + Room Number + Arrival Date + Departure Date + Representing + Mailing Address + Bus. Phone + Home Phone + Number Of Occupants + Additional Occupants + Vehicle Description + Special Instructions * Represents all of the infomration about customers in a certain room.*
Date = [01 | 02 | .. | 12] + \ + [01 | 02 | .. | 31] + \ + [1996 | 1997 | .... | 3000] * Represents the date in month/day/year format.*
Delivery Time = Time + Date
* The Time at which a room service request should be delivered.* Departure Date = Date
* Represents the date the customer is expected to leave.*
Employee = Employee Name + Password + Employee Number + Access Level * Represents all of the information on a current employee.*
Employee Name = Name
* Represents the name of an Employee *.
Employee Number = INT
* A unique employee number.*
First Name = STRING (30)
* Represents A Persons First Name.*
Food Description = STRING(256)
* A Field used to Describe a Menu Item.*
Food Item = STRING(32)
* A Field which represents dish on the menu item.*
Front Desk Messages = {Message}
* Represents all of the messages currently at the front desk.* Guest Bill = Guest Name + (Room Service Bills) + (Phone Service) + Arrival Date + Departure Date + Room Rate + Room Number + Amou nt Paid + Balance + Method Of Payment + (Credit Card Number) + Employee Number * Represents all of the information needed to generate a bill fo r a guest.* Guest Name = Name
*Represents the name of a Guest*
Handicapped = [Yes | No]
* This field determines if the room is Handicap Accessible.* Home Phone = Phone Number
* Represents the home phone number of the customer.*
Hotel Rooms = {Room}
* Represents all of the rooms in the hotel.*
Last Name = STRING (30)
* Represents A Persons Last Name.*
License Plate = {[ 0 | 1 | .. | 9 | A | B | .. | Z]}^9
* Represents the license plate of a vehicle.
List Of Food Entries = {Menu Item}
* A particular order of some items off of the menu.*
Mailing Address = Street Address + City + Province + Country + Zip Code
* Represents A postal mailling addres.*
Menu = {Menu...
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...The Entity Relationship Diagram (ERD) depicts a conceptual data model that incorporates some of the important scientific information about the real world. It adopts a natural view that the real world consists of entities and relations (Chen, 1976). One objective of the ERD is to create a simple, easy to understand and conveniently presented data model consisting of entities, attributes, relationships and
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Chen published one of the first articles on the entity-relationship model in 1976 at a database conference (Chen, 1976). The concept of entity-relationship already existed for years in the field of philosophy and began to be applied to database design heavily between 1975 and 1980. In 1979, there was a conference on the entity-relationship model during the First International Conference on Entity-Relationship Approach in Los Angeles, California. Annual conferences on the topic continued until 1995, when the conference was renamed the International Conference on Conceptual Modeling (AICCM, 2003). The entity-relationship model is the...
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...Basically an Entity relationship diagram is mainly purposed on the use of different types of modeling such as conceptual and logical. Through an entity relationship modeling, it ensures the nature of the entity and how data of an entity is used. This diagram is made in such a way that anyone could understand the basic process of the entity which means, none of the
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...Chapter 1 The Entity Relationship Modelling The Concepts of Entity Relationship Model 1.1 Entity Types
? ? A group of objects with the same properties, which are identified by the enterprise as having an independent existence. Entity occurrence is referring to a unique identifiable object of an entity type.
Figure 1.0 Example of entities with a physical or conceptual
Relationship Type
? ? A set of meaningful associations among entity types. It is a set of associations between one or more participating entity types. Each relationship type is given a name that describes its function.
Relationship Occurrence
? ? It indicates the particular entity occurrences that are related. Consider a relationship type called ‘has’, which represents an association between branch and staff entity. Each occurrence of the ‘has’ relationship associates one branch entity occurrence with one staff entity occurrence.
Figure 1.1 A semantic net showing individual occurrences of the has relationship type
Relationship Types
? A relationship of degree two is called binary.
Figure 1.2 An example of a binary relationship
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-------------------------------------------------
Top of Form
Bottom of Form
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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 conceptual and semantic model – captures meanings rather than an actual implementation
The E-R Model: The enterprise is viewed as set of
* Entities
* Relationships among entities
Symbols used in E-R Diagram
* Entity – rectangle
* Attribute – oval
* Relationship – diamond
* Link - line
Entities and Attributes
Entity: an object that is involved in the enterprise and that be distinguished from other objects. (not shown in the ER diagram--is an instance)
* Can be person, place, event, object, concept in the real world
* Can be physical object or abstraction
* Ex: &John&, &CSE305&
Entity Type: set of similar objects or a category of entities; they are well defined
* A rectangle represents an entity set
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ii. System Architecture
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While designing database it’s handy to have notation to “sketch” schema s Two common diagrammatic notations:
UML diagrams (Universal Modelling Language) ER diagrams (Entity
Relationship) → cs1106 choice
Captures the information requirements of our database: what data it con and how these interrelate
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o Entity-relationship modeling is logical
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This Hospital also can use Object-Oriented model.
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2. Do there appear to be any weak entities in the description of the Mountain View Community Hospital data requirements? If so, what are they?
No weak entity. However, treatment can be a week entity.
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I'm trying to create a database but in the design process. A bit of background on what is required. I have a table containing a bunch of details concerning customers. This is being imported from an external csv file every month. The data is going to be validated checking the email is valid and then copied to another table in the exact same structure but containing the details that are valid (valid email).
This data being imported is from an online registration (including name, DOB, email) form where customers choose their favourite genre styles based on external data of a list of pre-selected genres. There about 11 genres (also in a csv file). Also in this imported customer data is what each customer has chosen as a recently purchased magazine. This also comes from a magazine csv file with list of the magazines and a contact detail at the publisher.
Using this data I want to based on the customer data link between the music genres and magazine lists for third party suppliers who can view mailing lists and potential customers.
I've attached a jpg file of the erd diagram. I'm having trouble make sure the links between entities are correct.
I think you're on the right track.
Invalidated listeners to Listeners is 1 &-> 0..1
Listeners to Genres: 0..n &-> 0..n
which can be represented as
Listeners to Listener Genres: 1 &-> 0..n
Listener Genres to Genres: 0..n &-> 1
and same thing for magazines
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