Questions tagged [erd]
Entity Relationship Diagram
28 questions
15
votes
3
answers
9k
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Modeling a scenario in which each Music Artist is either a Group or a Solo Performer
I have to design an entity-relationship diagram (ERD) for a business context that involves the delineation of music artists, as I will detail below.
Scenario description
An Artist has a Name, and ...
- 151
14
votes
2
answers
3k
views
Best data modelling approach to handle redundant foreign keys in a database about Surveys, Questions and Responses
I am looking for advice on the best relational modelling approach to store surveys, questions, and responses.
I am looking for which of the two approaches below looks best, or an alternative approach ...
- 295
21
votes
2
answers
22k
views
Implementation of a many-to-many relationship with total participation constraints in SQL
How should I implement in SQL the scenario depicted in the following Entity-Relationship diagram?
As it is shown, every A entity type occurrence must be related to at least one B counterpart (...
- 375
8
votes
1
answer
21k
views
Ternary relationship: what's the difference between having single table and having multiple tables?
Consider the following ternary relationship:
Suppose that all entities have only two attributes (PK and Name).
Here are the tables I derived (5 tables):
Sector
-------------------------
ID_Sector ...
- 265
5
votes
1
answer
3k
views
ERD for a web development company
I am working on an ERD which represents the relationships between entities in a Web development company behavioral model.
There I have entities like:
Customer
Service ----------- (like: web ...
- 157
3
votes
1
answer
10k
views
Representing a Superclass/Subclass (or Supertype-Subtype) relationship in a MySQL Workbench diagram
Situation
I am trying to figure out how to represent a one-to-one (1:1) relationship regarding a superclass/subclass or supertype-subtype structure in an entity-relationship diagram (ERD) of the kind ...
- 33
2
votes
0
answers
886
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 ...
- 15
0
votes
1
answer
216
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 ...
- 5
31
votes
10
answers
2k
views
What is an effective way of labeling columns in a database?
I used to label columns in my databases like this:
user_id
user_name
user_password_hash
To avoid conflicts when joining two tables, but then I learnt some more on how to alias tables, and I stopped ...
- 511
9
votes
1
answer
30k
views
How can I import the contents of an Oracle database into Visio to create an Entity Relationship Diagram?
I have an Oracle database, and I would like to create an ERD in Visio 2007 Pro.
I have so far looked at DBMS_METADATA.GET_DDL commands to generate DDL. I know that I can import an Access DB into ...
kg.
8
votes
3
answers
8k
views
Which one is an ER diagram?
I have started to study ER diagrams. When I browse through the ER diagram tutorials, I found something like figure 1:
Figure 1
I tried to create a sample ER Diagram in MySQL Workbench like:
Figure 2
...
- 183
7
votes
1
answer
2k
views
How to model a Letter Transportation business context in a database diagram?
I am trying to crate entity-relationship diagram for a transport company database. This database should store information about letters, deliveries, moving letters from one warehouse to another, and ...
- 173
7
votes
2
answers
2k
views
Design: How do you decide when items are related vs when they are attributes?
I've been trying to figure this out for a while. Let's say you have a person, for example. An attribute of a person is his or her social security number, right? But a person also has a social ...
- 209
6
votes
8
answers
63k
views
How to export an ER diagram from an Oracle DB? [closed]
I am developing this application with an Oracle database. I haven't been documenting the data model, but now an auditor wants to have an entity relationship diagram of my database. There are many ...
- 1,285
6
votes
1
answer
808
views
Entity-relationship diagrams and application program functionalities
It seems that the core functionalities of an application program I'm working on are nothing but associative entities. Hence one-to-many relations sort of produce "metadata" that will only feed (one ...
- 335
5
votes
3
answers
1k
views
how do I model this in database?
I am using mysql as my backend database. Here is the use case;
A HolidayPackage is configured with some default offerings. These default offerings can be up/downgraded based on the options provided. ...
- 267
5
votes
2
answers
30k
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Can a weak entity have a primary key?
Sorry for probably a very basic question, but in the literature and online, I have came across two different definitions of weak entities, which may sometimes be contradictory.
1) Weak entity is an ...
- 153
4
votes
1
answer
13k
views
Entity set that has a relationship with itself
I have this ER model that I am having difficulty understanding, since there is an entity set that has a relationship with itself. I am trying to understand two questions:
1) Can a child be born ...
- 43
3
votes
3
answers
4k
views
Database design: 4 types of users but have different functionality , separate or one table?
I have 4 types of users:
Admins , normal user , company , service provider
Admins and normal user share some attributes (id .first name ,last name ,phone ,mail) company and service provider share ...
- 31
3
votes
1
answer
1k
views
Ternary Relationship or (n-ary)
I'm trying to find the difference in terms of modeling a ternary relationship v/s a binary relationship in the following case. Any piece of advise would help me a lot.
Company has editors who are ...
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 "...
2
votes
1
answer
883
views
Conversion of simple ERD to Table: is the solution below any good?
Consider the following ERD:
Suppose that all entities only have two attributes: a PK plus a name/number.
I want to convert that ERD to tables.
Is it needed 4 tables (1 for each relationship plus ...
- 265
2
votes
1
answer
4k
views
Bicycle Sharing Scheme - ER Diagram [closed]
Please compare the directions below to my ER Diagram and tell me if anything is wrong with my ER Diagram Please I think its accurate enough.
Oxford City Council is preparing to launch an innovative ...
- 19
1
vote
1
answer
19k
views
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 ...
- 336
1
vote
1
answer
499
views
When to use a multidimensional relationship in an ERD?
When to use a multidimensional relationship in an ERD? My textbook is in Dutch, and the two paragraphs that explain about multidimensional relationships is too vague and brief. I don't understand when ...
- 125
1
vote
1
answer
3k
views
How much the decision to use ternary or binary relationship influences the accuracy of the model with regards to a given business model?
The question title is very long, so here's a little bit of context to (try to) make it clear.
I asked a question regarding ternary relationship. The question was Ternary relationship: what's the ...
- 265
0
votes
1
answer
291
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 ...
-1
votes
1
answer
215
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 ...
- 111