Questions tagged [erd]
Entity Relationship Diagram
398 questions
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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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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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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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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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291
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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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1
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378
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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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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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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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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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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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4
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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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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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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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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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Are these two ERDs the same? Do they represent the same thing? [Weak entities and multi-valued attributes]
What I want to create is a table in a database for employees in a company.
Each employee has a unique identifier ID and a name. Each employee also has a list of skills, the skills are represented as a ...
Squidward_Dabbing
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1
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215
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What is the correct way to organize tables for a SQL view?
I'm new to data modeling. Currently working at creating a personal contact manager but I need some help with modeling the table relationships for a given view.
The final view columns I'm shooting for ...
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291
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How can I categorize entites by their age in an entity relational diagram?
I am designing an entity relational diagram and I need to categorize entities in groups by their age.
What I have is an entity of Person and some personal attributes about it. But I want to have ...
user226621
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How to model weak entity in ER diagram?
I was going through the weak entity concepts and was trying to model the relation Hotel has many rooms. I have come up with the partial solution presented below but i'm having a problem to uniquely ...
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2
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265
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multiple entities that share a table
I have this situation where i have two different entities, Researcher and Lab Manager and i want for a both to have a profile.
When a user logs in he could be one of the two entities, and searching in ...
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1
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What will be the relation between Employees and Players, given that some players are also Employees?
I have a requirement where I need to store information on Employees in a company that owns(?) a sports team and also store information on Players from other teams that are not Employees of this ...
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Help needed to design an ER diagram [closed]
I want to design an ER diagram in order to create a database for a small local business. My problem is that the bussiness sells merchandise to persons and businesses both. How can i differentiate ...
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Designing User & its Sub User Database Diagram Problem [duplicate]
There are some business category e.g. Travel Agency, Hotel, Car Rental etc.
Roles:
Management rolesSuper Admin, Staff
Customer side roles are Owner, admin and sales counter
May be etc. customer side ...
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216
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B2B application: users has its own users
B2B Scenario I am trying is that:
The following Roles exists in the system:
Super Admin
Super Admin Staff
Owner (client)
Admin (owner i.e. client and creates admin to define sales counters)
Sales ...
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1
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272
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ER Diagram Design
I need Help in making ER diagram that i made a ER diagram of each seperate or making it combine I made it seprate as image attached but how to combine and make it one ER diagram.
Module – 1: User ...
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1
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60
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Non-product invoice items
I am having difficulty representing additional charges in an invoice. I understand how to represent the association between an invoice and individual items in that invoice with the use of a ...
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2
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Anonymous and Public User Table Design in twitter like application
I have schema design problem which I am not 100% sure if my assumptions are correct.
So the requirements are:
I need to have 2 different type of user, anonymous and public.
A user can have both ...
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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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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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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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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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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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"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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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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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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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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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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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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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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1
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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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544
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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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How do I 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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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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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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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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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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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 ...
