Questions tagged [erd]

Entity Relationship Diagram

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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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41 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?
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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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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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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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1answer
47 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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41 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 ...
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30 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 ...
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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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59 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 ...
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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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38 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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531 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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Meaning of inverted vs non-inverted ISA triangle in EER diagram

I found two different ISA triangles in various books. Like one is inverted triangle(in first figure) and another is non-inverted triangle(as in second figure). Are they give the same meanings? I am ...
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39 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, ...
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39 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 ...
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56 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 ...
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20 views

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 ...
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56 views

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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23 views

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 ...
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590 views

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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22 views

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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35 views

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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27 views

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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1answer
54 views

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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35 views

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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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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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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2answers
63 views

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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248 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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693 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
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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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79 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
56 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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71 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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389 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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50 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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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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58 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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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
44 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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37 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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