Questions tagged [erd]

Entity Relationship Diagram

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18 views

Linking Subtype table to another table in EERD

I made this Enhanced Entity relationship diagram for my database project, but there is a problem that I have been mulling over. Over here, it can be seen that MANAGER is under the supertype of ...
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1answer
29 views

I need to put the data from the diagram in 3NF [closed]

This is a simple list table of a company trying to keep track of employee assignment to company projects (in other words, not a database but a flat one table file). You will design a database for ...
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0answers
28 views

What do these ERD relationship arrows mean practically? (One to one, zero or one to one)

So let's say we have this situation: I know this means that foreign key fk1 can be assigned to only one primary key id2 and likewise (meaning there cannot be duplicates of fk1 values in table1 as far ...
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1answer
176 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 ...
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1answer
20 views

Survey Database Structure

I am building a database to feed into a PowerBI dashboard. The data is extracted as CSV (SurveyResults) from Survey Monkey which will be loading into the MSSQL database. The outcome i am after is ...
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1answer
157 views

ESports League ERD

I'm creating a database for an esports league and am having some issues putting it all together for an ERD. Here's a quick rundown on how the game works: There are 2 teams of 5 Players each. These ...
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1answer
254 views

Should a TeamMembers table have a relationship with the Student Table or the Enrolment Table?

I'll keep it nice and short and simply link to the ERD: Users can be assigned a role, one of those is student. So for the sake of this, Students are the same as Users! A Student can be enrolled in ...
1
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1answer
56 views

“Diamond Shaped Relationship” What's the formal term?

Consider the following "Diamond-Shaped" entity relationship diagram: I'm trying to find some formal readings on why this is a bad design - but Googling "Diamond Shaped Table Relationship" only turns ...
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1answer
176 views

How do I model the following requirement in ER-Diagram?

I'm making a story-composer application which allows users to write stories and other users can contribute to it. A story can have multiple storylines and multiple levels(think like a tree or thread ...
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1answer
33 views

Database design for 'pay at table' product (integrating with restaurant APIs)

I am doing a database project for Uni and am trying to figure out how a 'Pay at Table' app would work for restaurants. I Have found this example company that does this https://readytopay.com/ but i ...
3
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0answers
33 views

ERD Cinema help [closed]

Im in need of some help. Most of all in the way i think when creating the ERD. I have searched online and asked some people but i think i formulate my question wrong which in turn confuses people. (...
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1answer
396 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 ...
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1answer
157 views

Understanding Enhanced Entity-Relationship Generalization Hierarchy Principles

I was given this exercise: (T/F and justify) It can be said that an entity related to another entity through a generalization hierarchy: a) will always have a total participation with ...
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1answer
27 views

What does this diamond shape represent in this ER diagram?

And what is testlog in this diagram is it attribute on relationship. Thanks
2
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1answer
328 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 ...
8
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2answers
20k views

Is it OK to have an entity in an ER diagram without a relationship?

I'm creating an ER diagram for a class assignment and I was wondering if it would be possible to create an entity that had no direct relationship to any other entity, and simply use foreign keys to ...
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2answers
176 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 ...
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0answers
48 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
411 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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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 ...
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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 ...
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1answer
40 views

ER Diagram Question [duplicate]

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 ...
0
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1answer
119 views

Covering and overlapping constraints

Given that there are 15 entities in E1, 20 entities in E2 and 25 entities in E3, what's the maximum and the minimum number of entities in E0? It's also known that the ISA hierarchy follows the ...
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0answers
80 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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2answers
55 views

How to Represent Equation with Variables in Relational Database

I am building an application to store the different formulas used for different subjects in school, and I have drawn the following database diagram to depict that scenario: I am having trouble ...
2
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1answer
43 views

ERD - Multiple FKs with only one of them being filled for each record

I'm designing a database schema for a music platform. Some of the entities as follows: track album band artist A "track" can have an "artist". It can also have a "band" which makes the artist ...
5
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2answers
12k views

Should ERD derived attributes be included in logical tables?

I have created my entity-relationship diagram (ERD for brevity) and it has derived attributes. When it comes to database design using a relational schema, I've designed my tables and linked ...
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1answer
204 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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1answer
169 views

How to create a SELECT statement involving a subtype

Okay, so all I'm trying to do here is "list" the managers who supervised the employee that charged a customer $100 for a rental on November 1st, 1998. My issue is that I don't know how to select the ...
2
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1answer
276 views

What do the entity-relationship diagram (ERD) symbols used in DBeaver mean?

I don't understand the ERDs used by DBeaver. The diamonds and dots at the ends of the line arent the crow's foot I'm used to. I've googled the subject and checked the docs but can't find a straight-...
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1answer
174 views

Hotel Booking Database design problem

I am currently designing (as an assignment for the course at the university) a database for online booking of hotels worldwide and I have stumbled into a problem. Here's is the conceptual design: ...
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1answer
174 views

How to create a correct entity-relationship diagram (ERD) about a video game profits scenario

I'm starting to build my application database, and I'm really new to the this world, so I have a lot of doubts about my ERD and if its entity types and relationships are ok. This is an application ...
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1answer
43 views

Help with an entity-relationship diagram re Manager entity type and its relationships

In the below ER diagram: A manager can have many Users but a User can only have 1 Manager A Manager must be able to assign multiple users to multiple courses Are the manager relationships correct?
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259 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
284 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 ...
2
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2answers
8k views

What does the Union sign in EER diagrams mean?

I know disjoint and overlapping, but what does the union like sign mean in an enhanced entity-relationship (EER) diagram...? For example: In other words, what does this diagram mean?
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143 views

Building an Entity-Relationship Diagram for a Language Dictionary

I need advice on how to build entity-relationship diagram (ERD) for Language Dictionary. Since I did not build ERD before, I will try to explain and show the ultimate goal of this project below. ...
6
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1answer
618 views

Entity-relationship diagrams and application program functionalities

It seems that the core functionalities of an application program I'm working on are nothing but associative entities. Hence one-to-many relations sort of produce "metadata" that will only feed (one ...
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1answer
25 views

modeling advice for table which may have 2 father tables

I am developing a ERP for a small cooperative with special needs (that'y why they need a non-general solution). I'd like to model the following: A "receipt" can either be incoming or outgoing For ...
2
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1answer
39 views

How to model a set of unique objects?

I have an entity type called 'Object', and I need to model an object set as a list of unique objects with variable length. Then, each object could belongs to many object sets. Current entity-...
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0answers
27 views

How to model this scenario in conceptual erd?Bridge entity needed?

I have a house-share entity( primary key : house-share id) and housekeeper entity (primary key: housekeeper id). At any point in time a housekeeper can only work in one house-share. When a ...
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1answer
76 views

Where to place derived attributes

I have an assignment which requires me to design a database. I have 3 entity types WARD, BED, and BED_ASSIGMENT (which is the "composite" entity type between BED and WARD). The BED primary key ...
3
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1answer
14k views

Number of ISA relationship triangles in an Entity-Relationship Diagram

The following two diagrams are nearly identical. However, in one, there are two ISA triangles from the Entity "Movie" and in the other there is just one. What is the difference in meaning?
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1answer
190 views

ER diagram to Relational Schema (Many to Many relationship)

In this ER diagram, can anyone explain how we should convert the many to many relationships ('view', 'update' and 'diagnose') to Relational Schema and then SQL? What I think is that there shouldn't be ...
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1answer
109 views

Need help with a table relationships and over-all design

My design is a Netflix clone which has movies and shows just like Netflix. There is also a table called transcodes which will have information on a movie or episode video transcode. My problem is, I ...
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1answer
50 views

How do I draw the erd to model this scenario?

Customers are billed for the cost for the activity itself and also any "extra" items which are used as part of an activity. So I have the customers entity (identified by customer id) and an item ...
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0answers
30 views

When do I create a separate entity when drawing conceptual models?

I have these 3 scenarios: Rooms located in a house are assigned a room number within that house - thus, for example, each house has a room number 1. Each room has a phone number etc... My guess is ...
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0answers
16 views

Convert IS A relationship into relational schema [duplicate]

I'm trying to map below IS A relationship into relational schema. Would there be two tables one for Savings account and one for Checking account each containing their own attributes? Or would there ...
3
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5answers
14k views

Automatically create ER diagram from database schema

I have a database with 193 tables and I need to create an entity-relationship diagram from them. There are no formal relationships between the tables with respect to FKs. The relationships are mapped ...
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1answer
55 views

Creating and querying a database to set hierarchical associations between Groups, Users, Items and Points

I am working with three entity types, Group, User and Item. A Group consists of Users, and a User consists of Items. Now, I have to work with a fourth entity type: Point. I want to be able to ...