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Questions tagged [erd]

Entity Relationship Diagram

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Database design of user setting

I have users who place Orders. There are some settings that user can decide and that can be applied at User level which means it will be applicable to all future orders that are placed by user or the ...
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0answers
15 views

Row level user privileges help with design [closed]

Say there are 2 tables Project and Task. How can I design Privileges table and assign permission like read/write/update/delete for each project/task from the above tables. Should I create two ...
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0answers
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Database Design , Is this Permitted?

Im working on a design for a database for school timetable and I need some help. So basically, the DB is made up of tables like teacher, student, subject, TimePeriod, and Classroom. I would just like ...
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31 views

Can an entity be an attribute of another entity?

For ER/EER Diagram: I have one entity Stadium and another entity Match. In Match entity I have the stadium as an attribute. The SOCCER database shall keep information about the stadiums used as ...
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1answer
61 views

EER Diagram - subclasses which are neither disjoint nor fully overlapping

Suppose we are writing an enhanced entity-relationship diagram (EERD) for a company's database. This company offers two services A and B. If the two services were disjoint, then this might look ...
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1answer
45 views

Setting up a many-to-many relationship based off of two other many-to-many relationships

I have 3 main top level entities: Project (PK: Id) Owner (PK: Id) Product (PK: Id) Here are the rules: A Project can have many Owners. An Owner can have many Projects. A Project can have many ...
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1answer
20 views

How to specify the domain of an attribute in an entity-relationship diagram (ERD)?

In an ERD (as in, rectangles for entity types, diamonds for relationship types, ovals for attributes, etc.) how would one specify that an attribute is, say, a 5-letter word?
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31 views

Syntax to establish a strong and weak entity relationship in MySQL? Weak entity's partial key is different from strong entity's primary key

The following image below depicts an entity-relationship diagram (ERD) of a strong and weak entity. The closest example, I found here (link), required that a foreign key be defined in the weak entity,...
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1answer
43 views

Does adding a surrogate key get rid of an identifying relationship between two entities?

In the following example, we have a Comments table with a composite primary key (PK) CREATE TABLE Comments ( video_id INT NOT NULL, user_id INT NOT NULL, comment_dt DATETIME NOT NULL, PRIMARY ...
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2answers
50 views

Modelling two dependent many-to-many relationships

I have a user who may have 0 or more foo's and bar's. Here is a diagram: Each foo has a unique integer ord. If a user has a bar, then this implies that he has a foo with ord=1. A user may not have ...
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3answers
94 views

Model multiple 1-m relationship to a single entity

I have an entity called Box. This box has a from property which could be from a variety of different entities. It could be from a user, office, import, storage and many more. So far I can think of ...
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1answer
46 views

Converting (a) an entity-relationship diagram about an airline booking scenario to (b) a relational schema

I am currently following notes on a certain "7 step strategy" to transform an ERD to a relational schema and was wondering some points about step 4, converting one-to-many (1:N) relationships. The ...
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0answers
25 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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1answer
69 views

How to generate Entity Relationship (ER) Diagram of a on-premises database using Azure Data Studio (macOS)?

I found a similar question for SQL Server Management Studio. But I use latest Azure Data Studio on macOS. We use on-premises SQL Server (not Azure cloud). How can I use Azure Data Studio to generate ...
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1answer
57 views

Designing a data model for a survey; building the relationships

Let's say I have a survey that will be handed out to many people. I have a hypothetical diagram with User, Question, and Response entities. Should my relationship be one-to-one from question to answer?...
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1answer
46 views

Entity-Relationship Diagram problem: trying to resolve a tentative many to many relationship

The case study states "each car belongs to a car type" and "each mechanic specializes in a car type or many car types". My current entity type definitions: Car CarType Mechanic My Entity-...
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1answer
77 views

How to maintain customer addresses for Orders?

The database I am designing is part of a project I am working on. I have come up with 3 simple "business rules": Customers must either be Individuals or Businesses (a business belongs to a certain ...
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22 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 ...
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2answers
78 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
146 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
68 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 ...
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1answer
25 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 ...
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1answer
44 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
83 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
204 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 ...
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1answer
290 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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114 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
36 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
130 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!
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1answer
235 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
140 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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1answer
646 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 ...
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0answers
28 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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1answer
73 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....
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1answer
22 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 ...
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3answers
299 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
83 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
44 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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2answers
62 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 ...
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0answers
896 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 ...
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1answer
51 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 ...
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0answers
142 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,...
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0answers
41 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 ...
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1answer
35 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
29 views

How to solve the problem with usage of messages at many places?

I'm developing an app, that provides games/quests for users. A Quest is something like a game and contains multiple Checkpoints. Every Checkpoint contains multiple Steps. Every Step either just ...
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0answers
44 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(...
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1answer
21 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 ...
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0answers
56 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?
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0answers
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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 ...
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3answers
453 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 "...