Normalization is the process of organizing columns into tables within a relational database in such a way as to minimize redundancy and avoid insertion, update and deletion anomalies.

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History table design for supertype/subtype

I'm designing an asset management database that tracks IT hardware. I decided to use a supertype/subtype design. I'm at a point where I want to track history of changes for devices. I wanted to use a ...
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66 views

Dependency preserving decomposition

Let be the following relational scheme: F={AB → C; AC → B; AD → E; B → D; BC → A;E → G} Is the following decomposition without loss of dependency? R¹=(A,B),R²=(B,C),R³=(A,B,D,E),R⁴...
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4answers
139 views

Row for each date, or 31 columns?

Currently I have a system whose front-end looks like this: The following query: SELECT `l`.*, `s`.`month`, `s`.`year` FROM `summarylines` `l` JOIN `summaries` `s` ON `l`...
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1answer
70 views

How to design tables such that a person can work for many companies? [closed]

Database design such that a person can work for many companies?
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394 views

Does my table violate normalization rules?

I am developing an emulator for a game. My item table looks like this: -- ---------------------------- -- Table structure for `items` -- ---------------------------- DROP TABLE IF EXISTS `items`; ...
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2answers
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Customer table with last order id - violate normalization?

So I'm looking at a customers table that has a relationship with an orders table. There is a trigger in place to set the last_order_id field of the customers table whenever a order it placed. Does ...
2
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1answer
129 views

What would be the Candidate key (s) of this relation?

R(ABCDEPG) F={AB->CD, DE->P, C->E, P->C, B->G} To my consideration, the candidate keys are: AB, AG, CD, DE. Am I correct? Why or why not?
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1answer
327 views

How to model schedule and keep good constraints?

I have some data that I am having a hard time modeling. Particularly, I am unsure of how I can ensure that I have unique data. This is for a schedule where I am assigning teams to stores. A team will ...
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3answers
237 views

is id and phone number enough to uniquely identify a row in phone numbers

Was designing a table a customer_phone_numbers table a while back, which only purpose was to allow us to store as many phone numbers as a user wanted to have on file. I originally came to the ...
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2answers
877 views

Modeling invoices and orders

I have a problem in modeling a database that contains orders and invoices. Actually it's more of a problem from a business point of view, but it's related to modeling the database nonetheless. Model ...
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2answers
303 views

Writing to a DKNF database, but reading from a de-normalized table for performance?

Would the following approach be reasonable? The Goal: queries have to be relatively fast, but without the hassles incurred by writing to a de-normalized database. The Context: A database for ...
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1answer
82 views

Minimal 3NF normalization issues

I'm trying to learn how to normalize to 3NF but the example that my teacher gave us doesn't really help. The algorithm I always used is this one: Find a canonical cover F_c for F For each FD X->Y ...
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98 views

What are the prime and non-prime attributes in this relation?

R(HIJKLMNO) L -> MNO HI -> JKLMNO J -> KL K -> H HI is a key. So, H is a prime attribute. But, H is also in non-key part. What are the prime and non-prime attributes in this relation?...
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56 views

Does schema normalization enhances query efficiency

I understand the importance of normalization in reducing data redundancy and various anomalies but I am wondering if it can also enhance the performance of your query?
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367 views

Can somebody help me normalise this database/check my workings

I am new to database design/normalisation and functional dependencies. I have started a new database class in school this week and we have been given a worksheet that requires the following: This is ...
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2answers
202 views

Normalizing nearly identical tables

Background I'm managing a relatively small database project in which we are adding support for reporting involving status updates for items in out product table. I was bit thrown into this and I've ...
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3answers
466 views

Database design for conditional detail table

I have an expense management system for monthly expenses. Expenses are of two types: one-time monthly expenses, and daily expenses for each day of month. I have created the following tables: ...
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3answers
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Simple scenario needs to go from Unnormalized Data to 3NF - Review Please

NOTE: The Question has been updated. View Edit Revisions to view original question. The scenario. An animal charity that at the moment, track their establishment's costs via a spreadsheet like so: ...
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248 views

design of maintenance database

Lets say i am designing a database that tracks maintenance of equipment. Each piece of equipment has various fields that usually don't change eg. ID, model, serial number etc. Some fields change ...
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1answer
1k views

Multilingual Dictionary Database question

Let's say someone is coding a multilingual dictionary in PHP, and he wants to let people submit both words and definitions in English and Spanish, but wants to track it so they can be filtered. ...
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1answer
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Are there any schema design changes that can take a design from 4NF into a different 4NF design?

My thought/contention is that once a database schema is in 4NF it by definition can only be changed into something less than 4NF (Denormalisation, 3NF etc) and that there is no alternative 4NF design ...
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1answer
98 views

Lost (and found?) on 4NF

I'm so extremely lost on 4NF it's not even funny. I've been reading on it for literally days and, except for about 15 minutes ago, I wasn't sure that I had even broken the surface. I think I might ...
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2answers
62 views

Table “normalization” and tradeoffs

It's been a while since my databases course in university, so bear with me as I try to be unambiguous here. In the domain I'm working in, there are Sources and Destinations. Both have 2D coordinates ...
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1answer
296 views

Data normalization (from 0NF to 1NF)

I am designing a relational database in mySQL - a library management system. I want to show examples of the data in 1NF, 2NF, 3NF, BCNF, etc. My example of 1NF looks something like this "A relation ...
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1answer
704 views

Dependency preserving and lossless join decompositions

I have a relation: R = {A, B, C, D, E, F, G, H, I, J} And a set of functional dependencies: G = {AB -> C, A -> DE, B -> F, F -> GH, and D -> IJ} I ended up decomposing into two ...
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1answer
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Confusion normalizing data to 3NF and transitive dependencies

I am currently in a Database class and have some confusion with normalizing to 3NF. I have one specific issue that was not addressed in class but appears in the book problems. For example I have R ...
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1answer
373 views

Normalisation of practise database [closed]

I am a newbie to database design, and I'm a bit confused about how to create a database with minimum redundancy. Suppose I have a table abc with repetition of data in it and no two rows are same. Now ...
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Relations, dependencies and normal form

I have some issues in understanding about relations and dependencies. I will show two examples and what I want to know: Assume the relation GTX {G,T,X} with the following dependencies: G,X -> T ...
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1answer
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Why is a Star Schema more normalized than a 3NF Schema?

According to Oracle's documentation, third normal form schemas "may require less data-transformation than more normalized schemas such as star schemas". I'm confused, I thought 3NF is the most ...
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299 views

Does this database table violate normalization rules?

I’m working with Access 2010. I’m developing a database for a public art program – we paint large scale murals on walls. The database tracks blank walls in the city as potential sites for murals. It ...
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1answer
82 views

This database has two foreign keys going to a single field, is it in 3NF?

Firstly, here is a picture of the database diagram generated by SQL Power Architect. I needed to create a user_id pair in order to match friend requests to users, but this has given me two foreign ...
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1answer
37 views

Should I create many ID for a same Person/entity in my DB?

In my model, I must store the name of the teacher of some kids and the classroom in which the teachers work, let’s say. All of the hundreds of teachers in the schools have 1 and only 1 classroom, ...
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1answer
99 views

I created a DB schema for a project relating to collecting comments for web pages, is relational the way to go and how are my relationships?

I'm curious if relational DB is the way to go, if the current relationships in the diagram make sense, and whether it will bode well for coding.
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1answer
53 views

Database Table Design

I would like to ask couple of questions regarding my schema table design. I have the following data coming from an external database where I do not have any control over it. PROD_NO PROD_NAME ...
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51 views

Why wouldn't I put the single preferred option into its own table, instead of having a 'Preferred' column?

In similar spirit to How to implement a 'default' flag that can only be set on a single row I would like to specify that, for any given list of possible names for a business, only one of the ...
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1answer
54 views

On modeling pairs with a possibly empty second element

EDIT: I've made the post significantly shorter. I hope it's more digestible now. Consider the following schema: CREATE TABLE X ( x TEXT PRIMARY KEY ); CREATE TABLE Y ( y TEXT PRIMARY ...
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3answers
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Database design for bookmark system

I am creating a bookmark system where people can save their bookmarks. Each user has its own personal page with bookmarks. A bookmark should have atleast one tag and max five. Each user can create ...
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1answer
128 views

To normalize or not to normalizde? (10 fields)

I'm helping someone to design a database and for a specific case I'm not sure. I have 10 fields - this will never change - that will always be filled and used in every query that could be coming up. ...
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1answer
2k views

Normalisation from 1NF to 3NF

I need some guidance on normalisation from 1st Normal Form to 3rd Normal form. I have already set up my database which is working fine but needed to show some normalisation to show that I did do some ...
2
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1answer
530 views

3NF decomposition + database normalization

I am studying for a test and would like to know if I am on the right track to get the following into 3NF with minimal number of keys for R: Given relation R(A,B,C,D,E,F,G) and the functional ...
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1answer
464 views

Multiple values in lookup fields

I know newer versions of MS Access allow multiple selections in lookup fields. For example, if I'm collecting information on my students, I can have a field called Race with lookup values that ...
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Looking for suggestions to model a database of Electrical Components

We have a database of electrical components and I am trying to make sure I have a good design. I am not a database designer (my comfort zone is designing with these hardware components), so I am ...
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Should I move repeating foreign keys into separate table?

Idea Users can upload lots of items and send them from processing. From the upload settings I can set a channel to which the uploaded items belong to. Channel is a separate entity. Currently I set ...
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28 views

Creating UNF for multiple actions

I am creating a database design for manufacture company for my coursework. The database design should be able to do these tasks: Buy items from suppliers. (M - N) Items are used for making products. ...
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Is there any literature on “re-normalisation” of denormalised data?

I'm involved in a project, the core of which might be generously described as "re-normalisation" of denormalised data. (To be fair, the initial implementation took only the first 90% of the time ...
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How To Manage Random Data Without Repitition?

We have a database design problem of a Learning System. Please can somebody help us ? These are the requirements : A person can register for a module which has "n" number of questions. The person ...
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0answers
52 views

Method to Obtain LossLess Join BCNF Decomposition

I have been told a way to obtain loss less join BCNF but I don't know how to calculate candidate keys(also called super key in some cases) and trivial Dependency. I have been given a relation R = (...
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100 views

Is the table in 3NF?

I am creating a relational database - a library management system. I want to show an example where I normalize the data from 2NF to 3NF. My example of 2NF looks like The definition of third normal ...
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205 views

Identifying functional dependencies

I'm having trouble understanding the logic in use for identifying functional dependancies. Looking at the sample relation below, I understand fd1 - fd3. But when I look at fd4 and fd5, its logic ...
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Problem with reaching second normal form in a database

I'm currently taking an Databases/Database server course as a part of my education, and for this week we have been assigned a simple project to complete. I'm facing a problem regarding normalization. ...