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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1answer
719 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.
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1answer
402 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 ...
18
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4answers
9k views

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 ...
4
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3answers
238 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 | ...
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1answer
654 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
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2answers
305 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 ...
2
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1answer
164 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 ...
6
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3answers
1k 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 ...
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1answer
745 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
256 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
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1answer
312 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 ...
5
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2answers
9k 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 ...
0
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1answer
911 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 ...
7
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2answers
886 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 ...