Questions tagged [erd]
Entity Relationship Diagram
392
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Designing fictional SQL Cruise ERD with correct relationships/crows notation
I am currently designing an ERD for a school project and have my intended first draft. I'm looking for some feedback as I am very new to designing ERD's and looking for some guidance and correction ...
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0
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27
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is this ERD(Entity Relation Diagram) is correct or not?
I am creating an ERD for my college project. can anyone tell me if my ERD is correct or not. if not then what are my mistakes.
I am creating this ERD from django app. I generated the UML diagram with ...
0
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2
answers
35
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in ERD of a system in which teachers evaluating other teachers of their departments how can i connect Teacher, evaluation_result entiy,
A teacher could be an evaluator and also be an evaluatee. How can I achieve this?
0
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0
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9
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ERD Design Question
I am currently working on my database module assignment and have completed the initial design of my ERD (Entity-Relationship Diagram). I would greatly appreciate your insights and feedback on the ...
0
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1
answer
52
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Deleting a row in one table should also delete the corresponding rows in another table
I have these tables: station and water_types. The user may only have one station, and if the user wants to delete the station, the corresponding water_types must also be deleted. In a station, there ...
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0
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7
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How can I make it so only entities with a certain attribute can participate in a relationship ER diagrams?
I am writing an ER diagram for a pet spa, with pet being an entity as a superclass with the disjoint connection to the subclasses of either cat or dog. A service they can partake in is a massage, but ...
0
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0
answers
20
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EER Diagramming - Are unlabeled specialization branches overlapping or disjoint by default?
My understanding is when documenting specialization constraints (i.e. Disjointness Constraint) in EER diagrams you label the subclass branches as "o" for overlapping and "d" for ...
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13
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How to represent that One entity is not a part of other entity in Conceptual ERD
In a conceptual ERD using crowsfoot notation, How can we represent that one entity is not considered as another entity? I think that if we don't connect these two entities in the ERD, then it is taken ...
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24
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Help needed with database design
I am designing a real estate database to keep records of plots (lands). There are many aspects to it like sale deeds, buyers, sellers, etc. But specifically, the bit where I've got stuck and need your ...
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1
answer
33
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ER Diagram for Missed Visits
I have to design an ERD for a hypothetical scenario. In the scenario, the nurse at a rural clinic needs to get summary data regarding patient visits so she can reschedule canceled or no-show visits.
...
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0
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1
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143
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Get ERD from my Redshift database
I am a newbie in database management/governance.
The problem: I have my companies Postgres RDB in AWS Redshift. So this is not a private project, but enterprise environment. I add new tables/columns, ...
3
votes
1
answer
69
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Need help with first ER diagram
This is my first time doing the diagram. My teacher isn't the best at helping out or responding to questions so I've come here to ask for further assistance. I think I've mostly got it correct, but ...
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2
votes
1
answer
205
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PostgreSQL partitioned table data model
I have created partition by range based on row_created_tmst for PostgreSQL table. Since partition keys needs to be part of the primary key in PostgreSQL, row_created_tmst is included in the primary ...
- 27
0
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1
answer
29
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ERD Review, Employee travel lump-sum payment based on rank
I'm building application for employee official travel with lump-sum payment based on the employee group or echelon they have and I need a little help how to store the data correctly, as the problem im ...
0
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0
answers
34
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ERD based on FE mockups review
I'm trying to create an ERD based on the FE mockups here: https://i.stack.imgur.com/gRMNq.jpg.
It's a multi-tenant database where a tenant represents a company. Azure AD is used for authentication. ...
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0
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38
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Desiging an erd for complex e-commerce
I've an e-commerce, with multiple product variants, the variants can have different prices and quantities, and the website can have multiple languages support even for product name and description ...
- 101
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1
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36
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What arrow is used to specify the relationship between a junction table and the FK tables [closed]
This is part of my first database design. I am unsure what type of arrow to use to describe the relationship:
The tables are parking space, parking space features, and features.
I am unsure of how to ...
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1
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1
answer
208
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How to count the number of relationships to a table in MySQL?
I am arranging an ERD diagram of an existing database with about a 100 tables, to add some structure to the process, how rank out the number of relations the tables have to each other?
For example, ...
- 135
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1
answer
553
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Create an ERD diagram from a set of SQL CREATE TABLE statements
We have a Snowflake database that does not maintain relationships between tables. The lack of relationships is not my decision and I have no control over this. I would like to generate an ERD diagram ...
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2
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3
answers
473
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Is it ok to have repeated values in some of the columns and similar columns in two separate tables?
I'm trying to create database in which I could store thousands of job postings. I put here 3 sample records of these job postings so that you could better understand how everything looks like:
Every ...
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0
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82
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ERD Review for Chipotle Order System
Attached is the ERD for my attempt at creating an ERD of Chipotles order system. I've been trying to learn how to make good ERD for database design and wanted to get some feedback.
I'm confused on ...
2
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0
answers
47
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One-to-One? or One-to-Zero-or-One?
Scenario: I am being asked to create an HR training tracker for employees of a business. in this database I am using two tables:
EMPLOYEE(EMPLID, LastName, FirstName, PrimaryEmail) with EMPLID as the ...
1
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0
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43
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Table for an Appointment App
experts,
I am building out an appointment scheduler application. I am seeking advice on how best to tackle this issue.
I am building out my ERD and I am the point where I will be creating a ...
3
votes
1
answer
509
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If an entity's primary key must contain a foreign key, does that make the entity weak?
I'm currently learning about strong and weak entity types in the context of RDBMS. While reading, I came across this statement:
"A weak entity is dependent on a strong entity to ensure its ...
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0
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165
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My relational schema and a few questions about relations and duplicate values in columns
I'm trying to create database in which I could store thousands of job postings. I put here 5 sample records of these job postings so that you could better understand how everything looks like:
Now, ...
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3
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0
answers
50
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Help Creating a 'Complex' ERD
I am stuck on how to represent the relationships I need correctly. I have a
Produce table. Each type of produce—e.g., 'lettuce'—has one or more quantity suffixes that can be associated with it, e.g., '...
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1
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1
answer
399
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How to implement disjoint (nonoverlapping) subtype with total completeness in MongoDB?
I designed an entity relationship diagram (ERD) with the goal of creating two child entities (INSTITUTION and SPACECRAFT) of a parent entity (LOCATION), which is distinguished depending on the value ...
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0
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646
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Can a foreign key be a primary key?
I want to know the relationship takes, teaches, advisors tables underlined attributes are foreign key or primary key? or both?
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0
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252
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Can I illustrate how a relationship depends on another in an ER diagram?
I'm new to data modelling and trying to build my first ER diagram for supermarket management. My current diagram is based on the following description which I myself come up with:
"Suppliers ...
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1
answer
68
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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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4
answers
93
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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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1
vote
1
answer
774
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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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0
votes
0
answers
620
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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 ...
1
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0
answers
126
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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 ...
0
votes
1
answer
101
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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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1
answer
40
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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
52
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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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5
votes
1
answer
2k
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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
123
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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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0
answers
993
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 ...
0
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1
answer
2k
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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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0
answers
844
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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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0
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374
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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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1
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17
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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 &...
0
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2
answers
179
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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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2
votes
2
answers
1k
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 "...
1
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0
answers
80
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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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0
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0
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734
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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 ...
0
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0
answers
61
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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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0
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1
answer
423
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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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