All Questions
Tagged with erd foreign-key
14 questions
-1
votes
1
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49
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What arrow is used to specify the relationship between a junction table and the FK tables [closed]
This is part of my first database design. I am unsure what type of arrow to use to describe the relationship:
The tables are parking space, parking space features, and features.
I am unsure of how to ...
- 1
3
votes
1
answer
870
views
If an entity's primary key must contain a foreign key, does that make the entity weak?
I'm currently learning about strong and weak entity types in the context of RDBMS. While reading, I came across this statement:
"A weak entity is dependent on a strong entity to ensure its ...
- 141
0
votes
1
answer
76
views
There are 2 ERD Designs, and one has a strange combination. I am told both are correct. why?
One of the designs seems clear: A REQUESTEDPRODUCT is picked from STOCK (which has many locations). The primary key is a composite key of 4 foreign keys.
The other design is more unclear. The "...
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0
votes
4
answers
103
views
Foreign key location
This is a question from a Master's degree.
What is the correct response to the question depicted in the image, and why?
Or do you believe there could be multiple correct answers?
- 1
1
vote
0
answers
99
views
Foreign key or copy of attributes in log entities
I am trying to design an ER for a system with the following specifications:
Each user has an account
The user can link his/her bank accounts to his/her account in our system
The user can deposit or ...
- 111
0
votes
2
answers
89
views
Multiple Primary-Foreign Key connections between Tables Redundant?
I have two tables, Reviews and Critic
I'm pretty new to RDBMS and I was wondering if the connection between Review.rID and Critic.Review is redundant?
My reasoning is that a single critic can have ...
1
vote
1
answer
19k
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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
2
votes
2
answers
1k
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Which table gets the FK? Is there a clear Parent-Child relationship here?
I have the following tables:
Each ProductLine will encompass many Parts. For this reason, it initially seemed to me that the Part table is a child of the ProductLine table. However, a part is not ...
- 179
1
vote
1
answer
2k
views
Clarification on Cardinality and Participation
I'm currently redesigning a schema with 20 or so tables and my first task is to create an ERD from the existing tables/constraints/relationships. This has proven more difficult than I expected because ...
- 121
2
votes
2
answers
130
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Enforcing existence of records while avoiding circular references
I'm having issues designing a satisfactory solution for the following problem.
There are two main entities:
Customer
User
A customer can have many users associated to it. A user can be associated ...
- 173
6
votes
3
answers
5k
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How to model Parent -> Child -> Grandchild if the Child can be removed
I'm dealing with a set of relationships where the child can be removed, but I obviously don't want to lose the connection between the grandchild and the parent. I did think about marking the child as "...
- 337
2
votes
3
answers
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 ...
- 135
1
vote
1
answer
909
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 ...
- 127
1
vote
1
answer
221
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 e_id
--...
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