Questions tagged [erd]
Entity Relationship Diagram
333
questions
0
votes
2answers
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.
...
-1
votes
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 ...
0
votes
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 ...
0
votes
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 ...
1
vote
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 ...
0
votes
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 ...
1
vote
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 ...
3
votes
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: ...
1
vote
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....
0
votes
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 ...
-1
votes
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
-1
votes
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 ...
4
votes
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-...
0
votes
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, ...
0
votes
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 ...
0
votes
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 ...
1
vote
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 ...
0
votes
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?
...
2
votes
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 ...
1
vote
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 ...
0
votes
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 = ...
1
vote
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 ...
0
votes
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 ...
0
votes
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. ...
0
votes
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 ...
1
vote
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 ...
0
votes
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 '...
0
votes
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.
0
votes
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 ...
0
votes
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 ...
1
vote
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:
...
0
votes
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 ...
0
votes
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 ...
0
votes
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:
0
votes
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 ...
1
vote
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, ...
0
votes
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 ...
0
votes
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 ...
0
votes
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 ...
1
vote
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 ...
0
votes
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, ...
-2
votes
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 ...
0
votes
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 ...
-1
votes
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
votes
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. (...
-1
votes
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
1
vote
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 ...
1
vote
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 ...
-1
votes
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 ...
1
vote
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 ...
