Category of database management systems characterised by the ability to join two data sets by matching on common fields, using mathematics-based relational logic.
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What is this type of query called, and how can I formulate it?
I have following tables:
events(event_id, name, description)
groups(group_id, event_id, title, description)
event_group(event_id, group_id)
users(user_id, name, email)
...
4
votes
1answer
107 views
How can I improve this design?
I'm creating an event planning PHP/MySQL web application as a learning project. The whole app revolves around the idea of the event and its various components (participants, groups, lists, etc.)
I ...
3
votes
1answer
227 views
How to use a relational database to store all users who belong to a group, and all groups which a user belongs to?
This is a beginner question:
A user can belong to many groups, and a group can contain many users.
Let's say the two tables look something like this:
user_id
user_name
user_email
group_id
...
2
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2answers
119 views
mySQL Relational Tables
Say I have 3 tables Products, Orders and Orders Product
Products Table
ID | StockNum | Description | Price
4 | 452SB | Black | 45.65
5 | 752SA | Green | 17.12
Orders Table
ID ...
6
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2answers
789 views
How do Application Like Yelp Retrieve distance information from data base efficiently
For example, say I have a table:
Business(BusinessID, Lattitude, Longitude)
All are indexed of course. Also there are 1 million records
Say I want to find businesses closest to 106,5, for example, ...
4
votes
1answer
229 views
Database structure, relational or data warehouse?
Good morning,
Im having some issues with how my database should be laid out and would appreciate some guidance. I have several tables (rainfall data), each containing the following columns:
Date ...
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0answers
492 views
ER to Relational Schema [closed]
I have developed an ERD diagram with UML notation in StarUML.
Now, I need to draw a relational schema but due to lack of features in StarUML i must use other tool.
My question is what exactly goes ...
4
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2answers
397 views
What's a good relational structure for units and complex unit conversions?
My company is in the Energy industry and I need to come up with a good way to represent the conversion of units of measurement. I've done some searching and have yet to find a good article covering ...
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3answers
230 views
Express union which is dependent on other results
I would like to make a union of two tables that are actually in a hierarchical constellation.
How would I write that in relational algebra? Say table A is the parent of B in a 1:n relationship.
...
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vote
1answer
318 views
Insert bulk Parent and Children rows using SQL Query
We receive bulk data from our customers in a spread sheet. I loaded them in a temporary table as of now. I tried to normalize the data and create a parent table and each parent to have 4 or 5 child ...
1
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1answer
576 views
database functional dependency candidate keys
How do you know when you found all the candidate keys in a functional dependency?
I know how i would go about finding a candidate key, just don't know how to tell if there are more.
Thanks.
4
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1answer
226 views
Would appreciate some suggestions on how I should model this data
I am setting up a website that will have users. Users can search for songs and (if signed in) save them to a playlist or their library of songs.
I want it to be like iTunes in that all the songs on ...
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4answers
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How should I design a relationship table for friendship?
If A is a friend of B, then should I store both values AB and BA, or one is enough? What are the advantages and disadvantages of both methods.
Here is my observation:
If I keep both then I have to ...
3
votes
3answers
200 views
How to design this simple DB?
How to design this simple DB?
I need to add some things to a DB I use to keep track of servers.
Table looks something like this.
Matrix
| Name | Description | Etc | Etc |
...
1
vote
1answer
347 views
Relational algebra question
Here is the relational schema given :
employee (person-name , street, city)
works (person-name, company-name, salary)
company (company-name, city)
manages (person-name, manager-name)
Q: Find the ...
6
votes
2answers
184 views
Definition for “logical difference”?
I'm currently reading "SQL and Relational Theory" by C.J. Date. And although I'm quite far in the book, I've got a few basic questions. I want to know what the term "logical difference" means, The ...
9
votes
3answers
950 views
Proper Use of Lookup Tables
I'm having trouble figuring out exactly how to place good boundaries for when and where to use lookup tables in a database. Most sources I've looked at say that I can never have too many but, at some ...
2
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1answer
132 views
How can I best combine “get categories” and “has user access”?
I was wondering if it's possible to create a query for the following problem. I only want to select categories from the (MySQL) database (if the user has access).
A user has multiple roles;
A ...
2
votes
2answers
188 views
Advanced search engine or server for relational database
In my current project we are storing big volume of data in relational database. One of the recent key requirements is to enrich application by adding some advanced search capabilities.
In the Project ...
6
votes
3answers
700 views
How to normalize Time Sheet data?
I am having a terrible time finding an appropriate way to store this data in a database.
The current excel (simple) version looks something like this:
http://i.stack.imgur.com/BEZOw.png
Staff and ...
4
votes
1answer
484 views
Two relationships to same table
i have one transaction table, each transaction has 5-6 contacts involved. each contact has the same fields like name, address, cell, email etc.
So the best thing I guess is to use the same contact ...
0
votes
1answer
518 views
Database design for head to head sports
I am trying to create a database to store details relating to darts matches. Im relatively new to this so was wondering if the design I've come up with below would work. It seems I have lots of places ...
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1answer
164 views
How to design relationships for variant data?
Help me define the table relationships for data with multiple structures. I need to track leads. Leads come from multiple sources. Each lead source has its own data structure. I need advice ...
3
votes
1answer
258 views
What scope(s) is “hasMany” a part of?
I realize, when talking about structures, obviously if you say "post hasMany comments" there are many records about comments relating to each post.
What I don't understand is what context these sort ...
4
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2answers
6k views
Relational Design - Multiple tables into one foreign key column?
Take a table that tracks meat purchases. It has a "meat_id" foreign key column to indicate what type of meat the purchase was.
But, the different types of meat are unique in some way (such as USDA ...
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1answer
684 views
Entity Relationship Model for linked tables
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 ...
5
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2answers
525 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 ...
