Entity Relationship Diagram

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table design approach for a rental application with several one to many relationships

I'm trying to go about designing a database/tables for the following situation I'm being presented. I'm developing a rental web application with MySQL as db engine. It is for a nonprofit organizations ...
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299 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 ...
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66 views

Issue with forming correct relationship between subtype and another table in ERD

The focus is on the Cashier table and the Cash Accountability table. The rule is that only Cashiers have Cash Accountability and a Cashier ideally only cashes out once per day. Before I changed the ER ...
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112 views

Database Design / ER Diagram - Help Needed

Please take a look at this ER Diagram that I started. I just don't know if I've set it up correctly (I have not made any relationships yet). I just want to know if I have the appropriate "Tables" or ...
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211 views

ER Diagram Issues

I'm currently working on a project and I just can't figure out how to setup the portion in "BOLD" and any help will be greatly appreciated. Oxford City Council is preparing to launch an innovative ...
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141 views

Does my ERD look well designed?

I am making a database at no cost for a local dance school. I'm still very new this would like to be sure that I designed it appropriately. From the front end, the parent will: fill out their ...
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130 views

How to get a surrogate key value in order to put a foreign key in and create relationship?

I am trying to create two relationships between three tables, using foreign keys with values of primary keys, which are surrogate keys. But I don't understand how to enter the right value in the ...
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101 views

Does an empty entity make any sense in an entity-relationship diagram?

I have an entity that has nothing else than a surrogate key as a primary key. I use it as an element made of a group of other elements For example : TABLE SchoolClass (classNumber INTEGER ...
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260 views

middle table in one-to-many relationships

I just started using mysql workbench but it is slightly from the er diagram that i design in paper. I want to have a 1 to many relationship with three tables. For example a have entity A and entity B ...
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55 views

ERD Design for Campground and Campsite

I am designing erd for campground and campsite. In general, a campground has many campsites in it. that lead to one to many relationships. but sometimes campsite has no campground, it appears as the ...
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838 views

Is an ER diagram an example of a conceptual, logical or physical schema?

I have been reading databases, and I clearly understand the difference between a conceptual, logical and physical schema. An ER diagram is an example of which of these schema's?
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224 views

How to model an “is a” relationship in an ERD using Crow’s foot notation?

I have to create an entity-relationship diagram (ERD) for an assignment. I am doing this in a particular drawing tool with the Crow’s Foot notation. There is however one thing I cannot figure out: ...
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Is the use of my lookup table efficient?

I'm trying to find the best way to architect the relationship in the scenario that: A team can have multiple players, a player may also have multiple teams My first thought was to use a lookup ...
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3answers
844 views

Help with a scenario of music groups and members in ERD design

Can someone please show me how to construct this ER diagram with the following scenario? I’m confused with the ‘or’ part of it. Description An Artist has a Name, and must be either a Group or a ...
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176 views

How to define User/Permission relationship as M:M?

The Resource relates to Action as M:M via Permission join table/separate entity. User can have many permissions. The same permission may be assigned to multiple users. How to define User-Permission ...
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2answers
152 views

New to databases - does my ERD reflect good database design?

I'm making a database to hold data for a media player that I'm working on. Originally, I thought to use one table with the fields: {filePath,artist,title,album,track_number,length,date,artworkUrl} ...
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51 views

Relationship issue

I'm working on a ERD with mysql workbench, and i have a little question. I have a Database with this tables: company_address country state city I want to store the address of the company with all ...
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346 views

What is the best way to represent an album and song entity in an e-commerce schema?

I'm designing a simple mp3(music) ecommerce site, customers can either buy a single Track or whole Album, an Album is made up of Tracks, so there is a one to many relationship between an Album and a ...
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55 views

Database table to keep track of objects

I have a table called FoodMaker and another table called Settings. Every FoodMaker has multiple Settings. I also need a 3rd table to record what has been made, when and with what Settings. It might ...
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48 views

Financial Inst - Model Role+Relationships b/w Person and Account

A Person can be on one-or-more Accounts. For each Account a Person is on, Person has a certain role on that account i.e. Person 1 is primary on Account 1 Person 1 is joint on Account 2 Person 1 is ...
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3answers
893 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 ...
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3k views

Cannot Add Foreign Key Constraint

Can anyone tell me why there are errors such as: Cannot Add Foreign Key Constraint And am I on the right track? My schema looks like this: DDL: DROP DATABASE ...
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281 views

ERD Design for Employee Leave

I found the following ERD design: Which trying to capture as much information about employee leave (i.e sick, travel, etc). What am trying to understand is what does the columns: Table : ...
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131 views

What would the relational diagram look like in this situation?

Situation Last week I had to do an assignment, and I did not agree with my teacher's ERD. She used a n-ary relationship while I used two binary relationships. I would like to know a true dba's (you) ...
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133 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 ...
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80 views

ERDs and modelling ownership of roles within Job table

I'm currently in the process of modelling what I see as a relatively simple relationship through my ERD. I'm not even certain that strictly speaking this is Many-to-Many but nevertheless there ...
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34 views

Completion of ERD, uncertainties about generalization/specialization and primary keys [duplicate]

I'm practicing making conceptual databases and I would like to know of I'm on the right track. I've been trying to create an ERD for a scenario as follows: A hotel can take bookings for weddings, ...
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3answers
557 views

Completion of ERD, uncertainties about generalization/specialization and primary keys

I'm practicing making conceptual databases and I would like to know of I'm on the right track. I've been trying to create an ERD for a scenario as follows: A hotel can take bookings for weddings, ...
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0answers
21 views

How to model mappings at various levels

I'm trying to design the database model for my application and I'm finding it difficult to design the mappings for user access to various entities stored in the database. If access was only ...
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1answer
5k views

Converted ERD into Dependency Diagram 1NF, 3NF

Thats the ERD. I'm studying for an upcoming test and having trouble getting my head around converting thes ERDs into dependency diagrams. This is from a previous exam that the Lecturer told us to ...
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3answers
321 views

Entity Relationship Model - double one to many

ERD A customer submits one or many leads. A lead belongs to one customer. A lead is a request or an inquiry. A lead belongs to one manufacturer. A manufacturer has one or many leads. Tables ...
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671 views

Relational Model Design - Entity with one attribute

I am trying to design a database relational model for an assignment. First, I design the ER diagram, and then the relational model with tables (schemas). Here's my question: Is it possible for an ...
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2answers
228 views

Is my ERD valid for airports,cities and airlines database?

My objective is to make a database of airports, cities and the airlines which provide coverage to them. I asked the question before on stackoverflow and the person told me to break up the ...
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159 views

Implementing a simple ERD in MySQL: is the implementation below 100% compliant with the ERD?

ERD Consider the following ERD: Tables From it, I derived the following tables: Company ------------------ c_id c_name ------------------ CompanyEmail ------------------ c_id ...
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1k 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 ...
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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 ------------------------- ...
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277 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 ...
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246 views

Relations between a imeid, sim chip, and account from a cellphone company?

I've never really had a cellphone (that I owned the account to...long story), but at work we have them, and we want to get a series of relations between accounts, devices (mifi's, tablets, ...
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598 views

Digital content eCommerce schema advice? [closed]

I don't have much experience designing databases, I'm looking for some advice on my design from more seasoned designers/developers. I'm developing a digital content eCommerce store which will be ...
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377 views

Can Anyone please review my database after I did the Normalization ?.Any suggestion is appreciated

User: User_ID,user_name,E-mail Staff: User_ID,Fname,Lname,DOB Student: User_ID fname Lname DOB Lecture: User_ID Admin: User_ID Position ID : P_ID,ROLE_NAME, Staff_position ...
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3k views

Db Design of a Room Booking System

I plan on building a web based room booking application for meeting rooms at a company. The requirements are not set in stone and are pretty much left to me, as long as these core ones are met: ...
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3answers
861 views

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 ...
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428 views

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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82 views

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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179 views

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 ...
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2answers
401 views

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 field 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 ...
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858 views

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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901 views

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 ...
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1answer
547 views

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 ...