Questions tagged [erd]
Entity Relationship Diagram
288
questions
0
votes
1answer
27 views
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 ...
1
vote
1answer
27 views
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 ...
0
votes
1answer
55 views
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 ...
2
votes
0answers
26 views
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 ...
2
votes
2answers
47 views
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 ...
2
votes
1answer
37 views
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 ...
1
vote
1answer
79 views
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-...
1
vote
1answer
84 views
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:
...
0
votes
1answer
28 views
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?
1
vote
0answers
62 views
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 ...
1
vote
0answers
82 views
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 ...
1
vote
1answer
42 views
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 ...
0
votes
1answer
24 views
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 ...
1
vote
1answer
124 views
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 ...
0
votes
0answers
82 views
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.
...
0
votes
0answers
24 views
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 ...
2
votes
1answer
39 views
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-...
-1
votes
1answer
55 views
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 ...
1
vote
2answers
79 views
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 ...
-1
votes
1answer
116 views
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 ...
1
vote
1answer
69 views
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 ...
0
votes
1answer
42 views
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 ...
0
votes
0answers
29 views
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 ...
0
votes
0answers
15 views
Convert IS A relationship into relational schema [duplicate]
I'm trying to map below IS A relationship into relational schema.
Would there be two tables one for Savings account and one for Checking account each containing their own attributes?
Or would there ...
0
votes
1answer
54 views
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 ...
0
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0answers
123 views
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 ...
2
votes
2answers
592 views
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 ...
0
votes
0answers
21 views
Database design of user setting
I have users who place Orders. There are some settings that user can decide and that can be applied at User level which means it will be applicable to all future orders that are placed by user or the ...
0
votes
0answers
59 views
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 ...
0
votes
1answer
167 views
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 ...
1
vote
1answer
48 views
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 ...
1
vote
1answer
23 views
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?
0
votes
0answers
104 views
Syntax to establish a strong and weak entity relationship in MySQL? Weak entity's partial key is different from strong entity's primary key
The following image below depicts an entity-relationship diagram (ERD) of a strong and weak entity.
The closest example, I found here (link), required that a foreign key be defined in the weak entity,...
2
votes
1answer
76 views
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 ...
0
votes
2answers
60 views
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 ...
0
votes
3answers
97 views
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 ...
1
vote
1answer
259 views
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 ...
1
vote
0answers
42 views
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 ...
2
votes
1answer
707 views
How to generate Entity Relationship (ER) Diagram of a on-premises database using Azure Data Studio (macOS)?
I found a similar question for SQL Server Management Studio. But I use latest Azure Data Studio on macOS. We use on-premises SQL Server (not Azure cloud).
How can I use Azure Data Studio to generate ...
0
votes
1answer
165 views
Designing a data model for a survey; building the relationships
Let's say I have a survey that will be handed out to many people. I have a hypothetical diagram with User, Question, and Response entities. Should my relationship be one-to-one from question to answer?...
0
votes
1answer
59 views
Entity-Relationship Diagram problem: trying to resolve a tentative many to many relationship
The case study states "each car belongs to a car type" and "each mechanic specializes in a car type or many car types".
My current entity type definitions:
Car
CarType
Mechanic
My Entity-...
0
votes
1answer
157 views
How to maintain customer addresses for Orders?
The database I am designing is part of a project I am working on. I have come up with 3 simple "business rules":
Customers must either be Individuals or Businesses (a business belongs to a certain ...
1
vote
0answers
36 views
Designing a message system
I want to create a messaging system but I'm stuck in the relationships between the sender/receiver of the message and the message itself.
This is a list of requirements for this system:
Allow both ...
4
votes
2answers
232 views
Should a composite primary key out of 3-4 attributes or a unique artificial ID should be used for the situation below?
For a small beginner project to start with databases and system development, I'm trying to develop a system that represents the classic case of an administration system for students and exams. This is ...
1
vote
0answers
305 views
Gaming shop database schema
I'm trying to design schema for my personal project that would be an online gaming shop. I would like to ask you guys for any suggestions/tips on how could I maybe improve my current draft.
Concerns:
...
4
votes
2answers
153 views
How do you read a one-to-many relationship in both directions?
I'm having issues with reading this relationship.
Let's take the Professor and Class entities in this example. If I read this from Professor to Class, I would say, "A Professor teaches one to many ...
-3
votes
1answer
31 views
I need help with normalising the data derived from a survey
Background information: I have been assigned to make a survey on E-sports and build a database. My survey can be accessible here https://devpatel6.typeform.com/to/MB1DYP . In brief, this survey ...
1
vote
1answer
145 views
Extended Entity-Relationship Diagram: Do the sub classes have foreign keys or primary keys?
Consider this example (they are disjoint, by the way):
There are two scenarios which I am guessing:
While translating it to relational tables,
the rows in PROGRAMMER are unique which do not exist ...
2
votes
0answers
148 views
Modelling a database for a simple IT device tracking scenario
Sorry, my English is not that good.
I need a simple IT device tracking sytem at work.
For each device I need to know its current location, status and ownership (employee to which it is assigned).
...
-1
votes
1answer
712 views
Is there an open source PostgreSQL IDE that allows for model generation? [closed]
I have done quite a lot of SQL Server work where I could use SSMS. Now I'm working with Postgres and I miss the ability to generate models (diagrams) from existing relations (taking into account ...
