Questions tagged [erd]
Entity Relationship Diagram
383
questions
-3
votes
0
answers
6
views
crow's foot notation to chen notation
how do I convert the crow's foot notation diagram below to chen notation?
0
votes
0
answers
17
views
Likes table with different types
I have an oversimplified database design where I wish to put all likes in the same table (only if it makes sense) .
A like, can be on either on a POST or on a COMMENT.
Options:
Distinguish the two ...
- 101
0
votes
0
answers
47
views
There are 2 ERD Designs, and one has a strange combination. I am told both are correct. why?
One of the designs seems clear: A REQUESTEDPRODUCT is picked from STOCK (which has many locations). The primary key is a composite key of 4 foreign keys.
The other design is more unclear. The "...
- 1
0
votes
4
answers
77
views
Foreign key location
This is a question from a Master's degree.
What is the correct response to the question depicted in the image, and why?
Or do you believe there could be multiple correct answers?
- 1
1
vote
1
answer
23
views
Chen notation to crow's foot
How do I illustrate relationships which has an attribute in chen notation to crows foot notation?
Example:
There is an attribute "quantity" in the relation. How do I draw that in crow's ...
- 11
0
votes
0
answers
16
views
Is there a command line tool to convert a SQL DDL file describing tables and relationships into a diagram?
Is there a command line tool that takes one or more SQL DLL files describing entities and relationships, and then transforms it into an ER diagram or something textual that can be turned into an ER ...
- 101
-3
votes
0
answers
28
views
Total hours spent on working on each project using SQL Server (Azure Data Studio)
Question:: Create a new view called “Project Hours” which would show for every project how many total hours were spent working on it, and the number of employees working on the project. Query the view ...
0
votes
0
answers
7
views
Is this ER Module correct
I am working on my first ER diagram for a case study. I wonder whether it is correct. I will include my case study here. It is really helpful if anyone can give me a feedback regarding my diagram.
...
0
votes
0
answers
18
views
Need help creating a transaction-grained fact table
For a personal project I need to design for the first time in my life a (star schema to keep it simple) relational database, the context is the sport of boxing.
Specifically, I need help designing a ...
0
votes
0
answers
17
views
Is this ER diagram correct?
I am working on my first ER diagram, for a clothing brand case study. I was wondering if my work is correct. Any feedback is more than welcome. My most important concern is the key relationships ...
0
votes
0
answers
14
views
Please review my ERD and SQL tables
it is about a carPooling app where any user can propose a trajectory that is divided into chuncks. Another user can construct his trip from available chuncks.
A user is identified by his mail. He can ...
0
votes
0
answers
15
views
ERD relationships rental_car
So I'm having difficulties with making an erd for a project about renting cars. I think I'm almost done, I only have to make the relationship between 3 tables ,2 of them had many to many relationship ...
- 1
1
vote
0
answers
17
views
Fashion Show ERD
working on a class project.
Have to make a ERD for a fashion show.
Not looking for a super in depth ERD, but one that will give a good grade.
I'd like it to be able to
Have a 'Clock-In/Clock-Out ...
0
votes
1
answer
49
views
Is my database ERD well designed
I'm creating a PostgreSQL database for datasets, which should store historical and future data of weather forecasts and train timetables. I'm wondering if my ERD is good enough for a database which ...
- 1
0
votes
1
answer
36
views
What is the correct usage of IN and ORDER BY keywords when used in conjunction with subqueries?
ERD for my simple db design:
I want to order children based on their parent's last name. I am trying to use the following query:
SELECT *
FROM children
WHERE parent_id IN (SELECT parent_id
...
- 127
0
votes
2
answers
18
views
Database Design for non-profit family assistance
I have a very basic ERD created for a simple database that stores some information about refuge families being helped out by a non-profit that helps provides some basic needs.
ID is the primary key ...
- 127
0
votes
0
answers
33
views
How do I adjust the table link endpoint in PgAdmin's ERD tool after autogenerating it from an existing database?
I can move the lines themselves around, but I can't move the endpoints, which cause the lines to overlap. The only way to understand which relationship is being referenced is by hovering over the ...
0
votes
1
answer
30
views
How should one design a logical data model for a social platform, or skip it?
After studying from 'Usage-Driven Database Design: From Logical Data Modeling Through Physical Schema Definition'a book by George Tillmann.
I want to create a logical model for a my own social ...
- 5
0
votes
0
answers
54
views
Entity relation with itself
I want to make an ER diagram for scientific research papers, one of the constraints is that a paper shouldn't cite itself.
I'm not very sure how to achieve this, as this question points out, the ER ...
-1
votes
1
answer
139
views
How to design a complex multi approval expense db schema in MySQL
I'm very beginner in database design and had the following problem to solve.
DB schema design for an expense approval system with these cases
approval system, every company has 1 or many teams where ...
- 49
0
votes
0
answers
60
views
When should I use associative entity?
I am studying DBMS and I have read that associative entity is used when there is a many to many relationships but I am confused with the graph. It has many to many relationships but did not use an ...
- 1
0
votes
0
answers
25
views
E-R diagram 1-to-1 mandatory relationship for two superclass entities to relational schema
How are two superclass entities that are connected to a mandatory 1-to-1 relationship converted to relational schemas? These two superclass entities are also abstract, meaning that they will not have ...
- 101
0
votes
1
answer
13
views
Convert generalization in ERD to Relationnal Database having no additional column
I've a quite simple problem but the litterature I came accross didn't seem to dwell on.
Let's say I have an entity OFFER which represents an Offer on a Product, for each product, one offer can be &...
0
votes
2
answers
32
views
ERD - How to add an attribute to one side of the recursive relation?
The simplified scenario for the ERD
A company has employees (each has unique id emp_id)
Each employee is supervised by another employee
A supervising employee has a special attribute SID
Here is my ...
- 45
0
votes
0
answers
32
views
Is it possible for a weak entity to be related to its identifying strong entity, as well as another non-identifying strong entity?
For context, I and a small group aim to design a game recommendation/search engine, and we ran into some problems designing the ER Diagram & translating said diagram into relational schema.
At ...
2
votes
2
answers
133
views
Primary keys due to inheritance
I am trying to design a database for postgrad office and we have a parent class "User" that has a username as a primary key for authentication and we have corresponding subclasses "...
0
votes
0
answers
21
views
Foreign key or copy of attributes in log entities
I am trying to design an ER for a system with the following specifications:
Each user has an account
The user can link his/her bank accounts to his/her account in our system
The user can deposit or ...
- 109
0
votes
0
answers
133
views
ERD to Star Schema
I have a simple ERD diagram as represented below for a supplier for inventory goods.
What would be the best way to turn this ERD into a Star Schema with one Fact Table and a few dimension tables?
To ...
0
votes
0
answers
27
views
Need guidance in creating an EERD
Hope I'm posting this at the right place. I have an assignment that I've been mulling over in an attempt to understand it completely.
Instructions
You are to create an EER diagram from the information ...
- 1
0
votes
1
answer
84
views
Entity-relationship for database design
Customers have the option to not provide a review or leave as many reviews as they want, but they cant have multiple reviews for the same product. How do I model this?
- 3
1
vote
0
answers
24
views
ERD related, can you make one to one relationship with a single attribute entity to another entity?
ERD Here
So for my database project, I designed a meat supply chain optimization project for a large organization, for example such as walmart, where every part of the chain is owned by the ...
- 11
0
votes
1
answer
31
views
How to re-design my relational model if there will be NULLs in one column?
I'm trying to build database which allow me store job postings from scraped websites and now I'm in phase of creating a relational model. Getting straight to the point I want to know how should I re-...
- 13
0
votes
0
answers
20
views
How would you graphically represent a relation between an associative entity and a subtype entity?
I need clarification and assistance in converting the following EER diagram to a relational schema, particularly the relationship between PERFORMANCE, an associative entity for PLAYER and MOVIE, and ...
0
votes
1
answer
38
views
Do I need to implement id column to table if i know that every added row will be unique? [duplicate]
I want to create database which allow me to store IT job offers from various websites. While creating ER diagram I started wondering if I really need an id column in one particular table. Look at this ...
- 13
0
votes
0
answers
49
views
Need feedback on my ER diagram
I want to create a database which allow me to store IT job offers scraped from several various websites. The problem is that job offers from these websites are not described in the same consistent ...
- 13
0
votes
1
answer
60
views
ERD for yearly budget ceiling advice
I'm working on webdev that involving yearly budget ceiling, but I can't wrap my head around to design such budget ceiling (my first project involving budgeting). So I need some advice.
So the scenario ...
0
votes
0
answers
15
views
Need clarification regarding my EER Diagram
I am currently building an EER diagram for one of my personal projects. It is regarding an e-commerce site that offers physical copies and streams of the movies. One of the requirements for the ...
0
votes
0
answers
19
views
Weak entity of weak entity
I wonder whether it is possible for a weak entity to have another weak entity dependent on it.
Specifically, I have a strong entity QUIZ which comprises of QUESTIONs unique to that QUIZ that I have ...
1
vote
1
answer
61
views
ER-Model to relational mapping
"Fundamentals of Database Systems" by Ramez Elmasri covers this topic extensively, I've gone through it and seemingly the rules mentioned aim at converting the ER-Model to a relational ...
- 11
0
votes
1
answer
60
views
Can a foreign key be used for two primary keys?
I'm still a beginner in sql and I have to transform this relation between clients and addresses and vendors and adresses. This uses 2 primary keys(1 for the vendors and 1 for the clients). My question ...
0
votes
1
answer
49
views
Is the database design alright? And I'm quite lost with the admin entity here
A quick description of my system would be: there are 2 users: users and admin.
User registers on the website. Upon registration, the system will generate a QR code for the user. The user then goes to ...
- 103
0
votes
0
answers
10
views
ERD where you can select multiple options/clarification multivalued attributes
This might seem like a stupid question but I want to make sure I get the basics right.
Lets say we have a flight with multiple flight options (such a seat selection, meals, extra luggage, etc.) These ...
- 13
0
votes
0
answers
150
views
Is my ER Diagram correct according this business rules?
Tiny Hospital keeps information on patients and hospital rooms. The system assigns each patient a patient ID number. In addition, the patient’s last name, first name, date of birth, and date of ...
0
votes
0
answers
21
views
If there is mandatory participation between 2 entities in an ERD, does this mean neither of them are strong entities?
Say I have entity A with primary key "key_A" and entity B with primary key "key_B”. I also have that key_A is a foreign key in entity B. My business rules state that every instance of A ...
- 1
0
votes
0
answers
23
views
Is My ER Diagram Correct?
I have a task to design database and problem is described as below:
I worked the problem and come up with my own design. sorry relations are overlapping I tried to make them explicit as I can
My ...
0
votes
0
answers
188
views
ERD for a simple bank system
I tried creating a simple erd for a banking system, I was wondering what can I improve, and where I did wrong. I'll also have to transfer this erd to sql and then try some queries on it. Thanks in ...
0
votes
3
answers
3k
views
Entity Relationship Diagram for Hotel
I tried creating an ERD model for hotel reservation and billing. Are the cardinalities correct, I'm a bit confused about that. And are there any attributes that are not in the right place? If someone ...
- 1
2
votes
1
answer
40
views
Question on EDR: a plant may have one or more harvesting seasons
I working on the following ERD, trying to understand what is the best way to connect the entities in the example of plants! For now I'm just focusing on the right side of the ERD (yellow, orange, ...
0
votes
2
answers
81
views
I'm trying to create a database for a hotel company with multiple hotels. I'm stuck on how to reserve a room?
I'm using Xampp phpmyadmin for the first time...
So I've got the basics of the database. Customers, hotels, rooms etc.
The customer can chose a check-in and check-out date.
An admin can class a date ...
- 1
1
vote
1
answer
68
views
Where to start learning the IDEF1X method of model notation?
I recently started learning about data modeling.
After seeing @MDCCL's diagrams and thoughtful approach here, I'm interested in learning more about IDEF1X. I don't want to pay $200+ for the ISO ...
- 111