Questions tagged [erd]

Entity Relationship Diagram

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12
votes
3answers
5k views

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 ...
11
votes
2answers
1k 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 ...
17
votes
2answers
10k 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 (...
5
votes
1answer
2k 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 ...
2
votes
0answers
80 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 ...
30
votes
10answers
882 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 ...
9
votes
1answer
27k 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 ...
8
votes
1answer
19k 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 ...
6
votes
8answers
59k 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 ...
7
votes
1answer
1k 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 ...
6
votes
2answers
761 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 ...
6
votes
1answer
618 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 ...
2
votes
1answer
677 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 ...
1
vote
1answer
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 ...
1
vote
1answer
309 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 ...
5
votes
3answers
886 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. ...
3
votes
3answers
2k 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 ...
2
votes
1answer
2k views

Bicycle Sharing Scheme - ER Diagram

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 ...