Questions tagged [erd]

Entity Relationship Diagram

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crow's foot notation to chen notation

how do I convert the crow's foot notation diagram below to chen notation?
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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 ...
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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 "...
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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?
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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 ...
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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 ...
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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 ...
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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. ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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2 answers
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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 ...
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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 ...
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1 answer
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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 ...
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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 ...
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-1 votes
1 answer
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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 ...
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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 ...
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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 ...
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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 &...
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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 ...
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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 ...
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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 "...
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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 ...
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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 ...
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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 ...
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1 answer
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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?
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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 ...
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1 answer
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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-...
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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 ...
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1 answer
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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1 vote
1 answer
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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 ...
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1 answer
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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 ...
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1 answer
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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2 votes
1 answer
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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, ...
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2 answers
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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 ...
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1 answer
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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 ...
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