Questions tagged [erd]

Entity Relationship Diagram

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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 ...
4
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2answers
423 views

Should a composite primary key out of 3-4 attributes or a unique artificial ID should be used for the situation below?

For a small beginner project to start with databases and system development, I'm trying to develop a system that represents the classic case of an administration system for students and exams. This is ...
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0answers
425 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: ...
4
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2answers
275 views

How do you read a one-to-many relationship in both directions?

I'm having issues with reading this relationship. Let's take the Professor and Class entities in this example. If I read this from Professor to Class, I would say, "A Professor teaches one to many ...
-3
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1answer
37 views

I need help with normalising the data derived from a survey

Background information: I have been assigned to make a survey on E-sports and build a database. My survey can be accessible here https://devpatel6.typeform.com/to/MB1DYP . In brief, this survey ...
1
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1answer
225 views

Extended Entity-Relationship Diagram: Do the sub classes have foreign keys or primary keys?

Consider this example (they are disjoint, by the way): There are two scenarios which I am guessing: While translating it to relational tables, the rows in PROGRAMMER are unique which do not exist ...
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0answers
181 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). ...
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1answer
827 views

Is there an open source PostgreSQL IDE that allows for model generation? [closed]

I have done quite a lot of SQL Server work where I could use SSMS. Now I'm working with Postgres and I miss the ability to generate models (diagrams) from existing relations (taking into account ...
3
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1answer
1k views

How can a weak entity be related to a weak entity?

As we can see in the entity-relationship diagram (ERD) below, the ATTENDANCE entity is related to the TRANSCRIPT entity. But how can entities in TRANSCRIPT be identified if there is no primary key in ...
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0answers
207 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 ...
1
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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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1answer
218 views

Entity-Relationship Diagram Software [closed]

I saw this E-R diagram in an answer on Stack Overflow: Does anyone know which software was used to create it? I use LucidChart but that output is really nice!
1
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1answer
718 views

Clarification on Cardinality and Participation

I'm currently redesigning a schema with 20 or so tables and my first task is to create an ERD from the existing tables/constraints/relationships. This has proven more difficult than I expected because ...
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0answers
179 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-...
4
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1answer
906 views

Designing a database which can track stock movements

I work for a manufacturing company which sells machines to customers which have a control unit installed in them. We need to keep track of the locations of all the Machines after they are sold to the ...
1
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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 ...
0
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1answer
98 views

Skip ERD in database implementation [closed]

AS we know that entity relation diagram(ERD) is an important concept in database implementation, But I was wondering that can we skip this step when creating a small database containing a few tables i....
1
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1answer
26 views

How to express a “some of which are” and “not all are” relationship with enhanced entity-relationship diagrams?

For example: Gardens have attribute gate, Condos have attribute door. Some of the Gardens and Condos are Private_Properties. On the other hand, Private_Properties are not restricted to only Gardens ...
1
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3answers
647 views

What can be best database schema for multiple project and one database? [closed]

I am working on multiple projects but the back-end will remain the same. I have a different server for auth, data, etc. and one database to store all the details. If one projects are creating any ...
2
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0answers
139 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 ...
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0answers
84 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 ...
2
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2answers
66 views

Enforcing existence of records while avoiding circular references

I'm having issues designing a satisfactory solution for the following problem. There are two main entities: Customer User A customer can have many users associated to it. A user can be associated ...
6
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0answers
2k views

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 ...
1
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1answer
69 views

Can i make a relationship between two relationships in the database?

I am making a database system where there are patients, doctors, categories and medical records. doctor and patient has a relationship called treatments ( many-to-many ) patient and a relationship ...
1
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0answers
239 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,...
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 ...
1
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1answer
44 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 ...
1
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0answers
48 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(...
0
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1answer
24 views

Basic Geometry Representation

I have an assignment in my introduction to database course. I chose to try and do a database model to represent basic geometric figures and mathematical objects (functions, polynomes, etc). For ...
1
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0answers
104 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?
3
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0answers
34 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 ...
6
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3answers
854 views

How to model Parent -> Child -> Grandchild if the Child can be removed

I'm dealing with a set of relationships where the child can be removed, but I obviously don't want to lose the connection between the grandchild and the parent. I did think about marking the child as "...
1
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1answer
71 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 ...
1
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1answer
1k views

Feedback on an entity-relationship diagram for a movie theater business domain

I have an assignment due next week, and for that assignment I am supposed to learn MySQL and create an entity-relationship diagram (ERD). My current attempt Now I've made this ERD The issue I ...
1
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1answer
527 views

Translating ERD diagrams into SQL DDL statements

I am currently establishing a database for Students and Courses using ERD. The style of ERD I am using is similar to the diagram below from the ERD Diagram Question: Note: The picture above is NOT ...
1
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0answers
200 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 ...
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0answers
25 views

How to track record on log_login when user can be deleted?

i really confuse to thinking my case. I design new db: tbl_user(id, name, created) tbl_log(id, user_id, action, created) //track user activity (delete, update, login, etc) what i'm confusing is to ...
0
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1answer
3k views

How do we express a weak entity to be dependent on another weak entity?

Perhaps I am looking at my entities as a hierarchy rather than a set of relationships; for sake of an example I have three tables: Authors Books Content Where Authors writes Books and Books contain ...
1
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1answer
765 views

Modeling an entity-relationship diagram about Clients, Orders, Payments and Bills

There is a part of an entity-relationship diagram creation that troubles me, I don't know if it's ok. I tried to follow these instructions: A client makes an order (which has products). When the ...
2
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1answer
41 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 ...
3
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2answers
336 views

Does my entity-relationship diagram reflect the relevant business rules?

I'm new to database design and I need some critiques, feedback, suggestions, advice, etc. regarding a) some business rules, b) the entity-relationship diagram I have developed to represent them, and c)...
0
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1answer
470 views

Foreign Key as Primary Key when “converting” conceptual entity-relationship elements to logical relations

Hi guys I'm trying to implement database models using MySQL. One thing struck me when I was trying to "convert" an entity-relationship diagram (ERD) to relations (or SQL tables). Note: Please keep in ...
-1
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1answer
418 views

Designing a database with a single valued attribute related to multiple entities

Here a customer can submit an order for one or many products . so, there is a one to many relation between customer_order and customer_ordered_products entities. Inside customer_ordered_products a ...
1
vote
1answer
571 views

What is an “operational master” with respect to entity-relationship diagrams?

I have a college assignment to create an entity-relationship diagram (ERD) for a database we're going to build. That's fine, but I have to include something called an "Operational Master" in the ERD. ...
2
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3answers
2k views

How to interpret ternary relationship?

I have tried to search online on how to interpret these ternary relationships but haven't found any clear answer. Since I don't understand how to interpret it I am having trouble changing it into ...
2
votes
1answer
309 views

Designing a Multiple Reflexive Relationship

I'm making a database diagram and I'm facing the situation explained below. Business rules: A device could have multiple connections with others devices (It's a graph). A device could be a server, a ...
4
votes
2answers
10k views

Can a weak entity have a primary key?

Sorry for probably a very basic question, but in the literature and online, I have came across two different definitions of weak entities, which may sometimes be contradictory. 1) Weak entity is an ...
1
vote
1answer
437 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 ...
2
votes
1answer
344 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
votes
1answer
793 views

Modeling a database for a printing company

Scenario Create a conceptual schema for the case study assigned to you using the concept of entity relationship model. Specify the cardinality ratio and participation constraint for each relationship ...