Questions tagged [erd]
Entity Relationship Diagram
398 questions
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Database design for bookmark system
I am creating a bookmark system where people can save their bookmarks. Each user has its own personal page with bookmarks. A bookmark should have atleast one tag and max five. Each user can create ...
user31574
6
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Automatically create ER diagram from database schema
I have a database with 193 tables and I need to create an entity-relationship diagram from them. There are no formal relationships between the tables with respect to FKs. The relationships are mapped ...
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Does my ERD account for my business logic
As part of my new and upcoming project, part of the business logic involves sending each and every one of my customers (assume they number in their 1000s) multiple (possibly customized) emails.
Each ...
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Data modelling concepts
Let´s say I have 3 entities. Can I have them all linked to each other "forming a circle" where each one is linked to the other trough a many to many relationship.
Cheers
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Can relationships have relationships?
I have the following requirements (as part of a larger system).
In the database, I need to maintain a list of parts, suppliers who sell those parts.
Many suppliers can sell the same part and each ...
- 253
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Number of ISA relationship triangles in an Entity-Relationship Diagram
The following two diagrams are nearly identical. However, in one, there are two ISA triangles from the Entity "Movie" and in the other there is just one.
What is the difference in meaning?
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Advantages of "middle" tables in one-to-many relationships
Entities:
Lists
Leads
What I am trying to achieve is a scenerio where in the relationship between lists and leads the following constraint is applied: A list can have many leads, but a lead can only ...
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What do you call a relationship between two entities without a foreign key?
Let's say I have two tables that are related in that one table contains a column that is a key to the other table. In other words, it would be a 1:1 or 1:* depending on constraints.
Let's call it an ...
- 143
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How to handle versions of an Entity in Database Design
I am working on a new project. The domain logic of the project is as follows:
A user uploads a file (Document) and gives a title, then another user comes along and (s)he also tries to upload a file ...
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3
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1
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Learning to draw entity-relationship diagram for a scenario involving Offices, Employees and Projects
I am trying to learn entity-relationship diagram, following question is the objective.
Information consulting firm has number of offices with employees. The employees can move offices depend on the ...
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The nature of the relationship between two tables in MySQL
Good day. I'm designing a database for a research project where we're predicting whether or not young female athletes will rupture their ACL(s) based on the nature of a test jump recorded with a ...
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Which is the redundant relationship in this ER Diagram and why?
Which is the redundant relationship in this ER Diagram and why? A few of my friends and I have been trying to figure it out but keep going in circles.
where the attributes of each entity are as ...
user2477979
2
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1
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4k
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Multi-variance products
My current system houses different variants of Products in different tables;
Productgroups
Productcolors
Productsizes
Productmodels
Products can reside under 1 Productgroup and can have multi-...
- 225
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2
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477
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Refactoring/normalization - but almost empty table
I normalized a legacy DB into this structure:
But I'm not sure if it is correctly normalized. I don't feel very comfortable with the almost empty filters table.
The requirements
A group contains ...
- 161
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ERD Review Please
I am building a simple database driven web application, but from reading so many books on the subject, I know that if my database is messed up, then my application too, will most likely be messed up.
...
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Drawing an entity-relationship diagram for a movie sales business domain
I want to keep track of movies that exist in different formats (for example, DVD, Bluray, etc.). The price for each format differs from the others as well as the quantity of each format, so I came up ...
- 149
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Payment methods conceptual and logical model
I need to create a conceptual and logical (normalized) models of parking house according to the requirements below. It looks to me as a very simple concept that doesn't need all tables to have ...
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How to model entities in an entity-relationship diagram about a car service scenario?
I'm a beginner Database designer and wondering if anyone can help me understand this.
Let's say we want to design a system that has, among other entities, an entity called Vehicle, and another one ...
- 364
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3
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Are there any tools to go from ERD to DB design and vice versa? [closed]
I'm learning DB design and looking for some tools, preferably open source software, that could help go from an ERD to a DATABASE and vice versa.
For the record, the database i'm using is MySQL.
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Should ERD derived attributes be included in logical tables?
I have created my entity-relationship diagram (ERD for brevity) and it has derived attributes.
When it comes to database design using a relational schema, I've designed my tables and linked ...
- 267
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409
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Users database to store access levels, can I move the non-essential information to another table?
I would like some advice on the best database structure for my system.
I have different kinds of users with different access levels, and different information of course. I created a users table with ...
- 101
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Modelling Relationships in an E-R Diagram, Table or Foreign Key?
Should a relationship in an E-R diagram be created in the database as a table or a foreign key?
For example:
a tutor lectures a class
I see it as three possibilities:
there is a "lectures" table ...
- 1,093
11
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1
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How are indexes represented in an ERD?
What do indexes look like in an Entity Relationship Diagram?
I've googled it and I'm unsure what the standard look of an index is in an ERD. And I'm talking about the crowsfoot diagram that includes ...
- 1,722
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How do I persist recurring events?
I've been tasked with designing a system to recur events. Events may recur daily, hourly, monthly or yearly. Users should be able to schedule events "every 3rd Wednesday of the month" or &...
- 3,934
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How do I create a user invitation model?
I am developing an application which allows 'users' to create 'lists'. I have a many-to-many relationship between 'users' and 'lists' (this might not be right). Additionally 'Lists' have many 'Tasks'. ...
- 247
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How do you represent VIEWS in an ERD?
Are VIEWS (CREATE VIEW) represented in an ERD? If so, how do you represent them and specify what tables they came from?
- 1,722
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Tool for Reverse Engineering of PostgreSQL Database on Linux (Ubuntu) [closed]
Please suggest a tool to reverse engineer a PostgreSQL DB into an entity-relationship-diagram (ERD) or equivalent ??
Ideally, I'm looking for a simple ERD or UML class diagram in a format that is ...
- 1,185
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How to translate high level entity relationship into schema
According to the following articles written by Dr. Chan, we can describe high level entity relationship. (see page-10,11 of doc-A and page9 of doc-B)
•doc-A) English Sentence Structure and Entity-...
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Is my ER Diagram correct? Why use relationships?
This is the first time I've made an Entity Relationship Diagram (ERD) for database that will be built on MySQL. The business domain of relevance is about equipment issues management.
Prior to this, I ...
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Entity relationship many to many
Is an association class in UML the same as an Link entity in ERD?
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Guidance on simplifying the following diagram
I have a case scenario where a customer can book accommodation or flight only or both.
I have modeled the accommodation part, however i am making things complex by over-thinking how stuff works in ...
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How can i model this data
A customer can make a reservation for an accommodation, the accommodation can be in a resort or elsewhere.
So i would say that a resort can have different types of accommodations, ie. Chalets, ...
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8
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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
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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. ...
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Suggest good ERD tool with UML notation [closed]
I need to design an ERD with UML notation, can anyone recommend a tool that does this.
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ERDs: How do you indicate mutually-exclusive encounters?
If you have a character_instance and character entity in an ERD for a video game, and you want to indicate that something happens when a character entity encounters a character_instance entity, how do ...
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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 ...
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ERD via Chen's notation: How do I organize multiple 'last done' entries?
I'm having an issue creating a little practice ERD. I'm trying to do some more difficult stuff, and I'm not sure what the standard way to organize it is.
Basically, I don't know which of these is ...
- 209
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Importance of ER Diagrams
I am a student and I am developing several projects as a part of my academia.
While developing the database for one of the projects, we came across a situation where we thought about whether ERD is ...
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Exporting from SQL Server 2005 for import into ER Studio 9.0
I am new to ER Studio and need to create an ERD for a remote system. That system can only be accessed by LogMeIn remote control and by FTP. The remote system is running SQL Server 2005. The local ...
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ERD directly producing 5NF relational schema - is this desirable?
I have been given a case study of Event Management. I have to develop an entity-relationship diagram (ERD), and based on it check if the resulting relational schema meets the different normal forms. I ...
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How can I generate an Entity-Relationship Diagram and SQL DDL statements from natural language text?
I am using LaTeX or another text-macro tool/library. How can I (1) use natural language text to describe relationships, then (2) generate an Entity-Relationship Diagram and (3) generate SQL DDL to ...
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Entity-Relationship Diagram for a scenario involving Books, Authors and Countries
Certainly a noobish question, but I'll ask it anyway. Perhaps someone else will be thankful. ^^
I am getting warmed up with MySQL and I try to understand the concepts of creating well structured ...
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When to apply normalization in database design
Prior to learning about normalization I would usually read the scenario/description in the requirements and draw up an ER diagram (using Chen's notation) using nouns as entities and verbs as clues to ...
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Is it OK to have an entity in an ER diagram without a relationship?
I'm creating an ER diagram for a class assignment and I was wondering if it would be possible to create an entity that had no direct relationship to any other entity, and simply use foreign keys to ...
user819
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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.
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How to structure a model to properly and efficiently represent tree-like data on relational databases?
Based on Traversing tree-like data in a relational database using SQL question, I would like to know how the way regularly used to describe tree-like data on relational databases considering physical ...
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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 ...
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