Questions tagged [erd]

Entity Relationship Diagram

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16 views

MySQL - Many to Many relationship, or one to many with additional columns

Our product contains some constraints that made us contemplate which table design will yield the best performance. Our model: Question table which contains fields like id, body, difficulty, and tags. ...
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1answer
36 views

Is my way of creating a entity relationship diagram correct?

From what I understand, 1)table customer and table order should have a one to many relationship since customer has orders. 2)table order and table payment should have a one to many relationship since ...
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1answer
21 views

How can instructors add users to their classes and at the same time not know all of the institution users?

I have the following entities Institutions - with institutionID and userID Institution Users - with institutionUserID Institution Classes - with institutionUserID, institutionID Institution Class ...
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1answer
31 views

Entity whose possible types differ in the FK

I have one entity called "Groups". "Groups" can be of different types and the difference between each type is the FK. For instance, if a "Group" is of type "Event ...
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2answers
39 views

Financial database model

I am completely new to database modelling (except for some academic knowledge from a long time ago) but for my new project I want to build a database for the following application. I am collecting ...
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1answer
25 views

“Tuples in a weak entity set are partitioned according to their relationship with tuples in a strong entity” - meaning?

http://web.cs.ucla.edu/classes/fall04/cs143/solutions/chap2.pdf In the above link, there is the following statement - "Tuples in a weak entity set are partitioned according to their relationship ...
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1answer
43 views

Weak entity having n instances as the 'one'

I'm struggling with a question, I'm just trying to figure is it even valid , if not where does it violates the rules of a weak entity relationship, I think it's not valid because how can a weak entity ...
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2answers
121 views

One and only one relationship - ER diagram to relational schema

I'm taking this term a DB course as part of my CS studies. This week we began studying the subject of ER diagrams, which I find a bit confusing. I have some uncertainty about the picture above (Note: ...
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1answer
45 views

Determining Cardinality in a Logical Model

How should one determine Cardinality in a Logical Model ? Should it be based on how the rows of an entity relate to another entity or should we consider the natural relationship between the entities i....
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2answers
27 views

Multiple Primary-Foreign Key connections between Tables Redundant?

I have two tables, Reviews and Critic I'm pretty new to RDBMS and I was wondering if the connection between Review.rID and Critic.Review is redundant? My reasoning is that a single critic can have ...
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1answer
11 views

ISA Crow’s Foot total participation

How to enforce total participation to ISA relationship using Crow's Foot notation? Like using a double line? _|_|_ \ISA/ \ / V
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1answer
32 views

Database scheme design for complex movie system

I'm creating a complex app for cinemas including frontend and reservation system. I struggle with a DB scheme and this is a worst part for me, I was never good in designing DB's. Easily said it's a ...
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0answers
56 views

Accounting database model

Need to build a service with an internal wallet function. Here is a simple use-case diagram: I have made a DB model But I don't like it for the next reasons No guarantee there will be only 1 sub-...
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1answer
32 views

Issues Designing ER Diagram

I'm trying to design an ER diagram in the relational database module of my course. We were given a scenario to draw a diagram for and then create a database within Access. I have the database covered, ...
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1answer
22 views

Domain of Attributes for an Entity?

I am new to DBMS and was reading about the ER Model and entities-attributes. I found the following line in the book which I was reading: The domain of Composite attributes is the cross product of ...
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0answers
12 views

MySQL: create ER diagram, but in text only

With MySQL Workbench it is possible to create a graphical ER diagram; however, this can become very messy when there are many tables and relations, so it might be good to have something like one or ...
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1answer
902 views

How to represent foreign key in an Extended ER Model in Chen notation?

This is a spin-off of the question at How to represent foreign key in an ER diagram? which is too vague about the needed notation. There the idea of underlining FKs with a dotted line is stated. I ...
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0answers
6 views

ERD - [range] : [range] relationship

Could someone tell how to give a description on the following relationship? One (or each?) Operator is managed by [how many?] Supervisors? And one (or each?) Supervisor manages [how many?] Operators? ...
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1answer
20 views

Modelling a relationship which has multiple one-to-many parents

I am attempting to model a relationship which could have two parents, one of them being optional, and the other being mandatory. The design should have the following rules, A House must exist as the ...
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1answer
338 views

Chat/conversation history, entity relationship diagram

Totally aware that there are very similar questions, went through each of them, but those are pretty simple/basic solutions from where i took some things and ideas to create below entity relationship ...
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0answers
25 views

Question about Ternary Entity Relationship Model

I can't wrap my head around these claims concerning this Ternary ER Model. Unfortunately this is in German so here are the translations: Prüfer = Examiner prüft = examines Fach = Subject Datum = ...
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1answer
75 views

Is it possible for total participation constraints to be enforced by an attribute?

For a school Food Delivery application I am developing, I've been told to use the most accurate ER model that captures as many constraints as possible. In particular, I have decided to enforce a given ...
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1answer
198 views

What is the Relationship between Instagram users and user followers

I'm building a blog project, which each user can follow other users. I'm still figuring out the design and creating the diagrams first. I know that the relationship between users and followers is many ...
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0answers
24 views

Simple ERD problem

I am a first year in university and just started learning simple concepts about ERD, was just wondering if a foreign key can be given to a table that has a minimum of one, maximum of one cardinality. ...
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1answer
116 views

Weak Entities + Partial Keys + 2NF [closed]

I'm a bit confused on the concept of weak entities and normalization and couldn't find any answers online. I know that generally weak entities have a partial key to uniquely identify its own records ...
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0answers
33 views

How to structure SQL data model to maintain data integrity

Background I'm building a Private Chef booking service where you can book a Chef to cook you a custom Menu. I'm having trouble creating a SQL db schema that accurately represents the domain while ...
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0answers
86 views

ISA-to-Table & Primary Key for Relationship Type

1).ER DIAGRAM TO RELATIONAL DATABASE 2).CAN A RELATIONSHIP TYPE HAVE AN ATTRIBUTE WITH A PRIMARY KEY? Can a relationship type have a primary key (primary attribute), like in the picture below? Can '...
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0answers
45 views

Use the following business rules to create a Crow’s Foot ERD

Is there any mistake in the ERD???? it looks weird.
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0answers
45 views

Strong Relationship Confusion on ER Diagram

In this ER diagram, there's a dashed line between the DAMAGE and RENT entities, signifying a weak relationship. But, as I understand, a weak relationship exists where one entity does not contain a ...
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1answer
37 views

Can someone give me feedback on my ER diagram?

I am new to creating ER diagrams and was wondering if anyone could review one that I constructed for an assignment. I used min, max notation in my design but I am not entirely sure if I did everything ...
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0answers
196 views

Food Delivery Service Database Design Questions

For a school Food Delivery application I am developing, I’m facing some problems during the ER model design stage. I have to fulfil many requirements but my main issues I’m having are the following: ...
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0answers
32 views

Need an ERD of the schema mentioned

Need the erd of the schema for doctor, patient and appointment database. scenario is given as under: Clinic Management Entity-Relationship Model -Doctor has a unique id, name, address, qualification ...
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0answers
48 views

What should the language dictionary database contain?

I am new to database modeling and design. I am trying to create a database for my project "Dictionary of Chechen Language". This could be an app where you can find out the translation into English and ...
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0answers
63 views

Depicting a Unique Constraint on a UML Diagram

I need to show on a diagram a unique constraint involving two attributes. For example, UNIQUE(COLA, COLB). This is what I have done:
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1answer
247 views

ER model for barber shop

My team and I are designing a database for a barber shop. The main focus of the project is to allow customers to schedule appointments with barbers for some sort of hair service. Our problem is that ...
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1answer
497 views

Alternatives to EAV model

I am looking for a design pattern that would allow me to capture metadata relating to columns on a table. More specifically, here is my situation. I have a database with fields in a field table, ...
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0answers
29 views

Basic holiday request database for university

I have been assigned a task to create a database ED diagram with the correct relationships for a annual leave request system which is being used at my workplace. Is this diagram correct? If not could ...
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0answers
19 views

Will a weak entity with two relations to two different strong entities use both of their keys?

I have to create an erd with three entities - customer, salesperson, and item. The customer and salesperson are strong entities, but the item is a weak entity. The customer buys the item and the ...
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0answers
11 views

Require relation for this business rule

Lots of games are played in each university location every year; but a game between any two universities is played at a given location only one time a year. Information collected about a game ...
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1answer
894 views

Does a weak entity always have a weak relationship and total participation in ER diagram?

I've found in some videos that say a weak entity has a total participation and weak relationship in er diagram. In other videos it isn't. I couldn't find a clear explanation for this. Please can ...
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0answers
25 views

ER Diagram: A relation is dependent on another relation

Take a look at the ER diagram here: ERD. This is a fragment of the whole ERD. I've included only the part relevant to this question. This somewhat hypothetical database has 4 entities. Course, ...
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1answer
235 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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1answer
79 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 the ...
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1answer
97 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
207 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
677 views

What does this diamond shape represent in this ER diagram?

And what is testlog in this diagram is it attribute on relationship. Thanks
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1answer
273 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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0answers
94 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
205 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 ...
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1answer
122 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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