Questions tagged [erd]
Entity Relationship Diagram
398 questions
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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 ...
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Use the following business rules to create a Crow’s Foot ERD
Is there any mistake in the ERD???? it looks weird.
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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 ...
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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:
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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 ...
user203653
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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 ...
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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, ...
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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 ...
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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 ...
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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 ...
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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 ...
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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. (...
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What does this diamond shape represent in this ER diagram?
And what is testlog in this diagram is it attribute on relationship.
Thanks
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"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 ...
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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 ...
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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 ...
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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 ...
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Covering and overlapping constraints
Given that there are 15 entities in E1, 20 entities in E2 and 25 entities in E3, what's the maximum and the minimum number of entities in E0? It's also known that the ISA hierarchy follows the ...
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Aggregation Vs Ternary relationship
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 ...
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How to Represent Equation with Variables in Relational Database
I am building an application to store the different formulas used for different subjects in school, and I have drawn the following database diagram to depict that scenario:
I am having trouble ...
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ERD - Multiple FKs with only one of them being filled for each record
I'm designing a database schema for a music platform.
Some of the entities as follows:
track
album
band
artist
A "track" can have an "artist". It can also have a "band" which makes the artist ...
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What do the entity-relationship diagram (ERD) symbols used in DBeaver mean?
I don't understand the ERDs used by DBeaver. The diamonds and dots at the ends of the line arent the crow's foot I'm used to. I've googled the subject and checked the docs but can't find a straight-...
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Hotel Booking Database design problem
I am currently designing (as an assignment for the course at the university) a database for online booking of hotels worldwide and I have stumbled into a problem.
Here's is the conceptual design:
...
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Help with an entity-relationship diagram re Manager entity type and its relationships
In the below ER diagram:
A manager can have many Users but a User can only have 1 Manager
A Manager must be able to assign multiple users to multiple courses
Are the manager relationships correct?
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Aggregation vs Ternary relationship - When to use?
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 ...
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Crow's foot notation--what is the difference between "one" and "one-and-only-one" regarding relationship cardinalities?
I'm trying to figure out the difference between the single-bar and double-bar cardinality indicators as in the figure below:
Some sources seem to use one notation while others use the other. I can't ...
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How to create a correct entity-relationship diagram (ERD) about a video game profits scenario
I'm starting to build my application database, and I'm really new to the this world, so I have a lot of doubts about my ERD and if its entity types and relationships are ok.
This is an application ...
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modeling advice for table which may have 2 father tables
I am developing a ERP for a small cooperative with special needs (that'y why they need a non-general solution).
I'd like to model the following:
A "receipt" can either be incoming or outgoing
For ...
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Which table gets the FK? Is there a clear Parent-Child relationship here?
I have the following tables:
Each ProductLine will encompass many Parts. For this reason, it initially seemed to me that the Part table is a child of the ProductLine table. However, a part is not ...
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Building an Entity-Relationship Diagram for a Language Dictionary
I need advice on how to build entity-relationship diagram (ERD) for Language Dictionary. Since I did not build ERD before, I will try to explain and show the ultimate goal of this project below.
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How to model this scenario in conceptual erd?Bridge entity needed?
I have a house-share entity( primary key : house-share id) and housekeeper entity (primary key: housekeeper id).
At any point in time a housekeeper can only work in one house-share.
When a ...
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How to model a set of unique objects?
I have an entity type called 'Object', and I need to model an object set as a list of unique objects with variable length. Then, each object could belongs to many object sets.
Current entity-...
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Where to place derived attributes
I have an assignment which requires me to design a database.
I have 3 entity types WARD, BED, and BED_ASSIGMENT (which is the "composite" entity type between BED and WARD).
The BED primary key ...
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How to represent the relationship between artists and albums in an entity-relationship diagram
I'm learning and practicing with the E-R model trying to design a music industry database.
With this section of the diagram I have a doubt:
I suppose an album can be had by an artist and a band, not ...
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ER diagram to Relational Schema (Many to Many relationship)
In this ER diagram, can anyone explain how we should convert the many to many relationships ('view', 'update' and 'diagnose') to Relational Schema and then SQL? What I think is that there shouldn't be ...
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Need help with a table relationships and over-all design
My design is a Netflix clone which has movies and shows just like Netflix. There is also a table called transcodes which will have information on a movie or episode video transcode.
My problem is, I ...
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How do I draw the erd to model this scenario?
Customers are billed for the cost for the activity itself and also any "extra" items which are used as part of an activity.
So I have the customers entity (identified by customer id) and an item ...
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When do I create a separate entity when drawing conceptual models?
I have these 3 scenarios:
Rooms located in a house are assigned a room number within that house - thus, for example, each house has a room number 1. Each room has a phone number etc...
My guess is ...
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Creating and querying a database to set hierarchical associations between Groups, Users, Items and Points
I am working with three entity types, Group, User and Item. A Group consists of Users, and a User consists of Items.
Now, I have to work with a fourth entity type: Point. I want to be able to ...
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Creating a Database for Multiple Calendars Support
I am trying to create a calendar application that can support multiple calendars, for instance Indian, Nepali, Russian etc. Users can enable or disable the calendars according to their needs.
I have ...
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Mapping a 1:1:N ternary relationship to a relational schema
I have a question about mapping (conceptual) n-ary relationships to (logical) relations.
Assume we have three strong entity types: Member, Equipment, and Time Slot, and a relationship named Reserves ...
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Can an entity be an attribute of another entity?
For ER/EER Diagram:
I have one entity Stadium and another entity Match. In Match entity I have the stadium as an attribute.
The SOCCER database shall keep information about the stadiums used as ...
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EER Diagram - subclasses which are neither disjoint nor fully overlapping
Suppose we are writing an enhanced entity-relationship diagram (EERD) for a company's database. This company offers two services A and B. If the two services were disjoint, then this might look ...
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Setting up a many-to-many relationship based off of two other many-to-many relationships
I have 3 main top level entities:
Project (PK: Id)
Owner (PK: Id)
Product (PK: Id)
Here are the rules:
A Project can have many Owners. An Owner can have many Projects.
A Project can have many ...
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How to specify the domain of an attribute in an entity-relationship diagram (ERD)?
In an ERD (as in, rectangles for entity types, diamonds for relationship types, ovals for attributes, etc.) how would one specify that an attribute is, say, a 5-letter word?
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Does adding a surrogate key get rid of an identifying relationship between two entities?
In the following example, we have a Comments table with a composite primary key (PK)
CREATE TABLE Comments (
video_id INT NOT NULL,
user_id INT NOT NULL,
comment_dt DATETIME NOT NULL,
PRIMARY ...
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Modelling two dependent many-to-many relationships
I have a user who may have 0 or more foo's and bar's. Here is a diagram:
Each foo has a unique integer ord.
If a user has a bar, then this implies that he has a foo with ord=1. A user may not have ...
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Model multiple 1-m relationship to a single entity
I have an entity called Box. This box has a from property which could be from a variety of different entities. It could be from a user, office, import, storage and many more.
So far I can think of ...
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Converting (a) an entity-relationship diagram about an airline booking scenario to (b) a relational schema
I am currently following notes on a certain "7 step strategy" to transform an ERD to a relational schema and was wondering some points about step 4, converting one-to-many (1:N) relationships.
The ...
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Cardinality with specialization in enhanced entity-relationship diagrams
I'm currently taking an introduction course to databases and I've come across a problem not described in the textbook.
I'm wondering about the use of cardinality with the use of specialization in ...
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