Questions tagged [erd]
Entity Relationship Diagram
398 questions
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If two entities are engaged in a many-to-many relationship with both entities participating totally, how many tables are needed?
I was thinking three tables, one for entity A, second for entity B and third for the relationship and describe the total participation in the third table by importing primary keys from first and ...
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2
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1
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917
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Drawing an entity-relationship diagram for a store business context
I have an entity called Users, with the attributes Id, Name, and Phone No. The objective is to develop an entity-relationship diagram (ERD for brevity) where Users might be Store Cashiers, and also ...
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3
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1
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Modeling a database for a printing company
Scenario
Create a conceptual schema for the case study assigned to you using the concept of entity relationship model. Specify the cardinality ratio and participation constraint for each relationship ...
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2
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1
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848
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Settle debate between Professor and Myself on interpreting Crow's Foot Notation in an ERD
I am taking an introduction to database objects course at college.
I am in disagreement with the professor over how to interpret the Crow's Foot Notation for Cardinality in an ERD diagram.
Example: ...
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6
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1
answer
808
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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
2
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0
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782
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How can I draw an entity-relationship diagram for a medical business domain?
I have to develop an entity-relationship diagram (ERD) for a business domain with the following characteristics:
A doctor consults from one clinic only, but a clinic may have many doctors working ...
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3
votes
1
answer
2k
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Parent and Child Relationship with the Same Foreign Table
Business Rules (I realize these rules are a little abnormal):
A Person (student) can attend multiple schools. Once one or more Schools are chosen, the student can pick one or more degrees at each ...
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-1
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1
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286
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Understanding Enhanced Entity-Relationship Generalization Hierarchy Principles
I was given this exercise:
(T/F and justify)
It can be said that an entity related to another entity through a
generalization hierarchy:
a) will always have a total participation with ...
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1
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0
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429
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Drawing a Entity-Relationship Diagram with No Relationships
As a school project I have made a small database with two tables, users and rooms.
users has two columns: username and password
rooms has room_name, room no, size
Can an entity-relationship diagram (...
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1
vote
1
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979
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Modeling a Recursive Association for Linking an Entity Type to Itself
I am designing a simple database as follows:
The database should contains an evolving set of standards;
each standard has a library of controls;
A single control in each standard may map to one or ...
2
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2
answers
58
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Is my schema right?
Is my schema correct? I tried this because my design plan is supposed to have repeating entries of offenses.
Something like this:
StudName | OffDesc
-----------+-------------
John | ...
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0
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290
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Concerns About Guidelines for Representing Nontransferable Relationships on an Entity Relationship Diagram
I am currently enrolled in the online Oracle Academy Database Design Course, which briefly talks about the concept of nontransferable relationships. I understand the concept behind them, but the ...
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1
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0
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How to get total cost of start package table between two periods by sql query?
Problem: how to get total cost of start package table between two periods with a SQL query?
alexaPackage from 28/06/2017 to 05/07/2017 8days cost ?
Details
I need to get total cost in start ...
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2
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0
answers
1k
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How can I model an ERD with relationships that include "this or that but not both" and "this and that"?
I am having trouble drawing a entity-relationship diagram (ERD) and I wanted to ask for any guidance on what I am doing wrong.
Busines rules
The descriptions of the assignment and of the business ...
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2
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0
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1k
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A Shop can have Products from a Supplier
I'm creating a Platform where Suppliers have Products that Shops can choose, add to their Shop and start selling.
My situation is as follows:
A Supplier can have many Products (for example: 'T-...
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3
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0
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2k
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Serialized Inventory Tracking
I'm developing a inventory system with optional serial no tracking (which users can turn on for items they select).
in order to keep stock records currently i came up with two options.
Option 01
use ...
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0
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1
answer
49
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Do I understand this relationship correctly?
So I made this bit of a diagram and I am not sure if I am going the right way in terms of understanding relationships. A character has attributes (Health, Mana, Power etc.) There are a quite a lot of ...
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0
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2
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464
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Entity-Relationship Conceptual Data Model [closed]
So I am busy learning databases for an rpg I have been thinking of to learn more specialized techniques with game development itself. Now I am trying to draw a conceptual data model to get things ...
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0
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1
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677
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how to get a schematic diagram/layout of the an existing database
I am looking for a schematic diagram of an existing database.
More precisely, I wan't to re-create the database model / schematics / the Entity Relationship Diagram (ERD) showing all the links between ...
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6
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1
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2k
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Postgres 9.6 export the database structure as pdf [closed]
Is there any tool/software the can export all the tables structure (column names , its datatype ) in the database as a pdf/excel/word. additional diagram export will be added advantage.
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Orders and Quotes Tables - Database Design
Below is the ERD of my current db schema for the orders part of an e-commerce site. The site is based on oscommerce, but has been modified, also I have removed quite a few of the fields from the ...
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2
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2
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3k
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Composite key as foreign key of multiple tables
On Entity1 table, could I merge the two "a" field in a single field ?
1
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1
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2k
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Can a sublass have two parents (two entity types that are connected with it?)
I'm kind of new to ERDs and stuff, just wondering if I'm correct when my (conceptual) entity relationship diagram has two entity types connected to one subclass (so the subclass inherits data from ...
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1
vote
1
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475
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What would be the correct entity-relationship diagram for this CSV file?
I received this from a customer and I was asked to model this as a database.
Key Article number color code description price action price delivery q1 size color
2800104 2 ...
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1
vote
0
answers
61
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Cardinality of one-sided and mutual authentication (entity-relationship modeling)
I would like to model client computers that are identified by servers that validate their computer certificates. I am stuck at the cardinality of the relationship between a client and a server when ...
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2
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0
answers
127
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How can you use an entity-relationship diagram to document business processes?
Past exam question: How can you use an entity relationship diagram to document business processes?
As far as I know, I would use an entity-relationship diagram (ERD) to document the relationships ...
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0
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1
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349
views
How do I model the following requirement in ER-Diagram?
I'm making a story-composer application which allows users to write stories and other users can contribute to it. A story can have multiple storylines and multiple levels(think like a tree or thread ...
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vote
1
answer
1k
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Do all entities in Chen notation have to be diagrammatically linked?
Is it good design practice to visually link each entity when using Chen's notation?
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0
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568
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How to resolve "unwanted" recursive relationship?
I'm currently designing a database for concerts, so I have created the following entity-relationship diagram (ERD):
Business domain characteristics
A concert can take place on a regular event or a ...
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1
vote
1
answer
365
views
How can I represent a relationship of cardinality many to many?
I'm trying to design a database for the information shown in the table
below:
In this regard, let's make the following assumptions:
Each Student may take many Courses
Each Course may have many ...
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0
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1
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32
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How to handle a many to many relationship with varying number of columns needed?
I'm designing a database that tracks hikes I have gone on. There is a Hikes table I have columns that include HikeID, LocationID, Type, Summit, #Friends. I then have a table called Friends which ...
2
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1
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2k
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What is a database mission-statement?
What exactly is a database mission-statement? My question was prompted after submitting an academic-assignment requiring a "mission-statement" for ERD-modeling. I've yet to encounter this ...
3
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1
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1k
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Crow's notation: Identifying relationships without the FK in the PK
I'm trying to wrap my head around the identifying/non-identifying relationships in Crow's Foot notation. I have read in most places that an identifying relationship means that the FK is a part of the ...
- 337
0
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1
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148
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How many tables are needed to implement the scenario depicted in my entity-relationship diagram?
How many tables are required to implement the scenario expressed in the ERD shown below?
My try:
Table (CR2) with the columns {B1, C1, C2}
Table (R1) with the columns {A1, P, B1}
Table (A) with the ...
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4
votes
1
answer
13k
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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 ...
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2
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1
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156
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Is it possible to represent a ‘mutual IS-A’ relationship in an entity-relationship diagram?
Is the following scenario correct and why:
A and B are two entities
B is-a A
A is-a B
And what if A, B were relationship?
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2
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1
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Subscription database ER model design
I'm designing a database for a review site.
There are products, and then for each product there can be multiple reviews.
I'm trying to add a subscription system, so that a user can subscribe to ...
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1
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Mapping Large Databases [closed]
I have the task of mapping a pretty large database schema (~250 tables). I can have Visio reverse engineer the database in pieces, but there are just too many tables to have it map the entire database....
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0
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1k
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Creating a Relational Products / Package Database
To prefix this, I am stuck using Microsoft Access, or at least relating to it, so my capabilities are a bit limited. I also do not want to use an EAV model. I could put the new tables into SQL Server, ...
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1
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Making an ERD of a movie database
I have a school project in which I have to design a database and my theme is Movie database of sorts. I created a basic ER diagram and I will post a picture here so you can tell me where are my ...
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3
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2k
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Should I define a FOREIGN KEY column as NULLable?
I've been developing some database structure to cover the following business rules:
An invoice has many invoice_items.
An invoice may have many refunds
A refund has many invoice_items.
All items ...
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4
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4
answers
13k
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How can I model a medical scenario in an entity-relationship diagram?
I am a self-taught frontend developer that is trying to go full-stack, so I am trying to teach myself data modelling by means of working on some exercises out of a database management book.
In this ...
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0
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1
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356
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Basic ERD question: how many entities to use
Say there are Buyers, Sellers, and Reviewers, all have common attributes to them such as:
name
address
login-info (username, password, email)
and all three have abilities unique to their roles.
e.g....
0
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1
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Converting EER diagram to ER diagram?
I'm studying for a database class and came across this EERD:
Very simple EERD however, I'm wondering- how can I go about and convert this to a simple ERD instead? From my understanding, the only ...
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1
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51
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Statistical Database Optimization
My friends and I are building a database for statistical research.
So we have a user that answers 10 questions in a row.
The questions are face-images, one is mirrored and the other one is the ...
5
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2
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1k
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How can I represent the entity types depicted in an ERD as relations with attribute names?
I have created the entity-relationship diagram (ERD) shown below (for brevity, each individual bubble-shaped box portrays multiple attributes):
Considering such an ERD, I have to convert each entity ...
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3
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2
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11k
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Multiple one to many relationships between tables
I'm creating a simple dabase design with three entities and have a question about the relationships between my Employee and Task tables.
The thing is:
A task has an owner, which is represented by ...
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2
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2
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112
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How To Add Days And Time For Instructor Schedule [closed]
Problem
I need to make a database design (ERD) to display a schedule for every instructor, including the following:
day of course (e.g. Saturday or Monday)
time it will give course (period from 12 ...
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7
votes
1
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2k
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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 ...
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0
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142
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Connect 3 or more entities
I'm new to data management. We are currently creating an ER diagram. First, I will ask a question and then give you an example.
Question
Can I connect 3 or more entities by one connection?
Task
...
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