All Questions
Tagged with erd relational-theory
15 questions
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
1
vote
1
answer
633
views
How to implement disjoint (nonoverlapping) subtype with total completeness in MongoDB?
I designed an entity relationship diagram (ERD) with the goal of creating two child entities (INSTITUTION and SPACECRAFT) of a parent entity (LOCATION), which is distinguished depending on the value ...
- 113
0
votes
1
answer
291
views
How can I categorize entites by their age in an entity relational diagram?
I am designing an entity relational diagram and I need to categorize entities in groups by their age.
What I have is an entity of Person and some personal attributes about it. But I want to have ...
user226621
0
votes
1
answer
161
views
"Tuples in a weak entity set are partitioned according to their relationship with tuples in a strong entity" - meaning?
http://web.cs.ucla.edu/classes/fall04/cs143/solutions/chap2.pdf
In the above link, there is the following statement - "Tuples in a weak entity set are partitioned according to their relationship ...
3
votes
2
answers
2k
views
One and only one relationship - ER diagram to relational schema
I'm taking this term a DB course as part of my CS studies.
This week we began studying the subject of ER diagrams, which I find a bit confusing.
I have some uncertainty about the picture above (Note: ...
- 33
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 ...
5
votes
2
answers
1k
views
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 ...
- 253
3
votes
3
answers
3k
views
Storing historical records and extracting data from a given period
This a question about database modeling and PostgreSQL. This post partially answers the question but I need advice on more technical stuff: columns and query to extract the data.
I need to store ...
- 317
1
vote
0
answers
187
views
ERD Diagram based on Crow's Foot model for Milky Way Jewelry
this was on my final exam this past winter exam season, in search for the answer since i got it wrong:
Draw an ERD diagram based on the Crow's Foot model for a database to support the basic ...
- 11
2
votes
1
answer
355
views
ERD to Relational schema
I'm new to DBM and I'm trying to learn it online. Honestly, I need some help with this. I don't know if I'm doing this right, and any help will be appreciated. This is my answer for i.
- 21
1
vote
2
answers
2k
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Trying to design database for eSports Teams - Issue with dependencies
I am trying to design a database in Access for an eSport league (specifically League of Legends North America). I will post what I have and then explain my issue.
My issue comes when I try to ...
- 11
4
votes
2
answers
6k
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 ...
- 157
2
votes
0
answers
1k
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 ...
- 123
2
votes
1
answer
3k
views
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
13
votes
2
answers
2k
views
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 ...
- 2,748