Questions tagged [erd]

Entity Relationship Diagram

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Working on a decision tree database design

I'm doing the conceptual model for a Decision tree database. The goal is store any Decision tree. I have four entity types: DecisionTree, Node, Branch and Leaf. Each Decision tree is composed of ...
5
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1answer
2k views

ERD for a web development company

I am working on an ERD which represents the relationships between entities in a Web development company behavioral model. There I have entities like: Customer Service ----------- (like: web ...
4
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4answers
5k views

How can I model a medical scenario in an entity-relationship diagram?

I am a self-taught frontend developer that is trying to go full-stack, so I am trying to teach myself data modelling by means of working on some exercises out of a database management book. In this ...
3
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0answers
33 views

How to design a database for my entity-relationship diagram about Projects, Tasks and Developers

I'm new to database and my entity-relationship diagram is as follows: According to that I designed my SQL-DDL database statements as shown below: CREATE TABLE Developer ( DeveloperID int NOT ...
3
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0answers
797 views

Serialized Inventory Tracking

I'm developing a inventory system with optional serial no tracking (which users can turn on for items they select). in order to keep stock records currently i came up with two options. Option 01 use ...
3
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0answers
797 views

ERD for a Contract between a Writer and a Publisher: Is it correct, can it be simpler?

I created an entity-relationship diagram (ERD) for a book publishing business context that I will detail bellow. Entity types The entity types of interest are: Writer Work (as a book) Publisher ...
2
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0answers
82 views

Aggregation Vs Ternary relationship

I am reading a book about database systems and in the chapter covering database design using ER, the author aims to explain when to use aggregation versus ternary relationship. In short, each Project ...
2
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0answers
178 views

Modelling a database for a simple IT device tracking scenario

Sorry, my English is not that good. I need a simple IT device tracking sytem at work. For each device I need to know its current location, status and ownership (employee to which it is assigned). ...
2
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0answers
132 views

Composite attributes in Barker notation

I would like to know how to draw set of entities with composite attribute in Barker's notation. In UML you can do this in that way: and in Chen's notation: Please, help. I have final exam day after ...
2
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0answers
42 views

Modelling a scenario involving architecture firms projects

I'm very new to Database Modelling (using the Finkelstein methodology) and I'm getting confused on a modelling scenario in particular. I am able to draw out the basics, however am running into some ...
2
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1answer
40 views

Troubles with an attribute that depends on the value of another attribute

I'm redesigning a health insurance costs database (actually they're not really insurance plans in my country but I think that for the sake of the example it doensn't matter). We're the health plan ...
2
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1answer
330 views

Drawing an entity-relationship diagram for a store business context

I have an entity called Users, with the attributes Id, Name, and Phone No. The objective is to develop an entity-relationship diagram (ERD for brevity) where Users might be Store Cashiers, and also ...
2
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0answers
474 views

How can I draw an entity-relationship diagram for a medical business domain?

I have to develop an entity-relationship diagram (ERD) for a business domain with the following characteristics: A doctor consults from one clinic only, but a clinic may have many doctors working ...
2
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0answers
627 views

How can I model an ERD with relationships that include “this or that but not both” and “this and that”?

I am having trouble drawing a entity-relationship diagram (ERD) and I wanted to ask for any guidance on what I am doing wrong. Busines rules The descriptions of the assignment and of the business ...
2
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0answers
493 views

A Shop can have Products from a Supplier

I'm creating a Platform where Suppliers have Products that Shops can choose, add to their Shop and start selling. My situation is as follows: A Supplier can have many Products (for example: 'T-...
2
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0answers
95 views

How can you use an entity-relationship diagram to document business processes?

Past exam question: How can you use an entity relationship diagram to document business processes? As far as I know, I would use an entity-relationship diagram (ERD) to document the relationships ...
2
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0answers
313 views

How to resolve “unwanted” recursive relationship?

I'm currently designing a database for concerts, so I have created the following entity-relationship diagram (ERD): Business domain characteristics A concert can take place on a regular event or a ...
2
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0answers
527 views

What is the difference between (Superclass/Subclass) Total and Partial Specialization?

What is the difference between total and partial specialization of superclass/subclass (or supertype-subtype) structures in enhanced entity-relationship modeling?
2
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0answers
108 views

ERD to SQL Server

I am working on an assignment and am having one heck of a time getting my head wrapped around these questions. I need to be able to write in SQL Server 2014 certain select statements based solely off ...
2
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0answers
483 views

Handling Strong and Weak entity types in a one-to-one relationship

I am modelling a database for a term project and I have come across something I do not have a definite answer to. Diagram I was supplied with the following Entity-Relationship diagram: Description ...
2
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0answers
1k views

What is a good database design approach for my Online Quiz Android Application?

I have been working on an Android Online Quiz Application with PHP & MySQL. I know what attributes i need however when designing the relationship it becomes complex and confusing when I analysed ...
2
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0answers
1k views

The nature of the relationship between two tables in MySQL

Good day. I'm designing a database for a research project where we're predicting whether or not young female athletes will rupture their ACL(s) based on the nature of a test jump recorded with a ...
2
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2answers
71 views

How To Add Days And Time For Instructor Schedule

Problem I need to make a database design (ERD) to display a schedule for every instructor, including the following: day of course (e.g. Saturday or Monday) time it will give course (period from 12 ...
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50 views

ER Relationship Total and Partial Participation Example

I am trying to understand partial and total participation. Given the statement: "Each restaurant must have one or more dishes and each dish must be provided by exact one restaurant." The below ...
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1answer
38 views

Understanding many-to-many ternary relationship sets

I am new to entity-relationship diagrams. I'm a bit confused when it comes to interpreting ternary relationship sets such as this: Does this signify that every relationship instance of Party will ...
1
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0answers
277 views

Aggregation vs Ternary relationship - When to use?

I am reading a book about database systems and in the chapter covering database design using ER, the author aims to explain when to use aggregation versus ternary relationship. In short, each Project ...
1
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0answers
290 views

Crow's foot notation--what is the difference between “one” and “one-and-only-one” regarding relationship cardinalities?

I'm trying to figure out the difference between the single-bar and double-bar cardinality indicators as in the figure below: Some sources seem to use one notation while others use the other. I can't ...
1
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1answer
183 views

Which table gets the FK? Is there a clear Parent-Child relationship here?

I have the following tables: Each ProductLine will encompass many Parts. For this reason, it initially seemed to me that the Part table is a child of the ProductLine table. However, a part is not ...
1
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2answers
183 views

How to represent the relationship between artists and albums in an entity-relationship diagram

I'm learning and practicing with the E-R model trying to design a music industry database. With this section of the diagram I have a doubt: I suppose an album can be had by an artist and a band, not ...
1
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0answers
60 views

Cardinality with specialization in enhanced entity-relationship diagrams

I'm currently taking an introduction course to databases and I've come across a problem not described in the textbook. I'm wondering about the use of cardinality with the use of specialization in ...
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0answers
37 views

Designing a message system

I want to create a messaging system but I'm stuck in the relationships between the sender/receiver of the message and the message itself. This is a list of requirements for this system: Allow both ...
1
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0answers
384 views

Gaming shop database schema

I'm trying to design schema for my personal project that would be an online gaming shop. I would like to ask you guys for any suggestions/tips on how could I maybe improve my current draft. Concerns: ...
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0answers
186 views

Modelling an entity-relationship diagram for a scenario involving companies, services, and clients

I am creating an entity-relationship diagram (ERD) for managing workflow and other details of Company X in which I am maintaining details of the following objects: Employees of Company X Services ...
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0answers
61 views

Creating an entity-relationship diagram about an art fairs and galleries business environment

Scenario description The charactheristics of the business domain under consideration are: Each and every art item has a unique identifying number, and also a name and asking price. Art galleries ...
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0answers
177 views

How to create entity-relationship diagram for tables that can potentially be united by an “IS A” relationship?

I have this schema: create table hall( building-id int, hall-id int, capacity int, primary key(building-id, hall-id) ); create table semester( sem-id char(5), start-date date, eend-...
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0answers
32 views

Local Transport Fare design: how to relate departures, destinations and locations

I am doing a conceptual model for local transportation fare app The goal is for users to quickly check the current fare and the previous fare from one location to the other. Sometimes, the ...
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0answers
81 views

ERD mostly in text

In LaTeX I can replicate database tables similar to the ones in the diagram below, but I do not want to deal with figuring out how to nicely draw the relation diagrams between the tables. Is there an ...
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0answers
237 views

Basic ERD analysis for a martial arts business domain

I am working on a basic website in order to support querying results from martial arts tournament data. We use participation data to determine things like who gets to host tournaments, regional awards,...
1
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1answer
43 views

How to make Event (like a Party) Sources mutually exclusive?

I'm designing an entity-relationship diagram (ERD) for a marketplace of events. An event can be created by a user, in which case the Event table must have owner_id or we pull it from an API in which ...
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0answers
47 views

ERD Design issue - general/central projects table

I have multiple different “project manager” apps as: Work Projects app manager, Home Projects app manager,... Each app has its own DB i.e separate ER diagram. Each app has it's own [projects] table(...
1
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0answers
102 views

How to draw an entity-relationship diagram with “at least” and “exactly” relationships

The business rules are: An order must have at least one product, and a customer must have created exactly one order. How can I draw an entity-relationship diagram for this?
1
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1answer
70 views

Entity-Relationship Diagrams: Identifying which way a relationship flows

I am having trouble grasping the "relationship" concept of an entity-relationship diagram. For example, you have Classroom and Furniture as your entities. If you were to put a relationship diamond ...
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0answers
199 views

Working on a scenario where two entity types have two kinds of relationship, one of which is ISA-to-ISA

I am a student of a university, and my teacher thinks my entity-relationship diagram (ERD) is weird. The ERD is about a ramen restaurant. The order receipt looks like this: Tofu Ramen $3 ...
1
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1answer
415 views

If two entities are engaged in a many-to-many relationship with both entities participating totally, how many tables are needed?

I was thinking three tables, one for entity A, second for entity B and third for the relationship and describe the total participation in the third table by importing primary keys from first and ...
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0answers
117 views

Drawing a Entity-Relationship Diagram with No Relationships

As a school project I have made a small database with two tables, users and rooms. users has two columns: username and password rooms has room_name, room no, size Can an entity-relationship diagram (...
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0answers
99 views

Concerns About Guidelines for Representing Nontransferable Relationships on an Entity Relationship Diagram

I am currently enrolled in the online Oracle Academy Database Design Course, which briefly talks about the concept of nontransferable relationships. I understand the concept behind them, but the ...
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0answers
53 views

How to get total cost of start package table between two periods by sql query?

Problem: how to get total cost of start package table between two periods with a SQL query? alexaPackage from 28/06/2017 to 05/07/2017 8days cost ? Details I need to get total cost in start ...
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0answers
50 views

Cardinality of one-sided and mutual authentication (entity-relationship modeling)

I would like to model client computers that are identified by servers that validate their computer certificates. I am stuck at the cardinality of the relationship between a client and a server when ...
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0answers
297 views

Creating a Relational Products / Package Database

To prefix this, I am stuck using Microsoft Access, or at least relating to it, so my capabilities are a bit limited. I also do not want to use an EAV model. I could put the new tables into SQL Server, ...
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0answers
73 views

Connect 3 or more entities

I'm new to data management. We are currently creating an ER diagram. First, I will ask a question and then give you an example. Question Can I connect 3 or more entities by one connection? Task ...