# Tagged Questions

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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### Database Normal Form (financial statement)

I would like some advice on how to design the database for financial statement data which objectively addresses the tradeoffs between usability, performance, maintenance and adherence to normal form. ...
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### 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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### Is it proper to make a grand-parent key, a primary key, in its grand-child, in a multi-level identifying relationship?

I'm modeling a DB for a conference ticketing system. In this system attendees are members of an attendee group, which belong to a conference. These relationships are identifying, and therefore FKs ...
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### Normal Form question

Hey guys I am trying to study for an exam and I cant seem to get my head around normal forms. here is one question: R1 [a b c] fd1: {a,b} -> {c} fd2: c -> b I know the candidate keys are {a,b} {a,c} ...
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### why this FD make 3NF?

Question like this: Consider the relation scheme ABCDEF satisfying the following functional dependencies: BC --> ADEF CD --> B E --> D BC is a key and designated as primary. Explain why the ...
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### Decompose Relation R(ABCDE) in 2nf and 3nf

Given relation R(ABCDE) with functional dependencies A->C B->D AB->E Given: AB is the primary key. I know that this relation is in 1NF because of partial dependencies A->C and B->D Now how I ...
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### Dealing with co-dependent not null columns

Say I have a table entities (subclassed by people and organizations tables), where each entry requires a primary_email_id. The entities table looks like this: entities ======== id INT AUTO_INCREMENT ...
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### How does one know when to stop normalizing?

Alright, so basically I feel that I tend to over-normalize things, and maybe I am doing it at the cost of performance. So, to illuminate on the problem, I have created the following schema to use as ...
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### Preventing duplicate data when usual normalization only makes sense for some of the records

Background I have two tables, one called issues and the other called status_checks, which both contain (among others) the field comment (VARCHAR). An issue is raised by a user when something needs ...
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### Need help about normalizing database to 3NF

I am currently working on a city travel guide application which let users explore places and plan trip. In the account module, the following functions are to be considered: User can register by ...
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### What exactly is overlapping candidate key?

Can some one please explain to me in simple terms what is overlapping candidate key ? What is overlapping as the name suggests? Consider the below relation R(L,M,N,O,P) { M -> O NO -> ...
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### Array column vs another table when the relationship is quite small

The Data I am creating a table of cities and their zip codes for the United States. Some zip codes have a list of acceptable cities, as designated by the USPS. For example, the zip code 36613 is ...
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### Transforming a relation to 3NF

I'm trying to transform the following relation to 3NF but can't figure it out. The relation is (a student can only have 1 major): STUDENT (StuID, StuName, Major), Primary Key = {StuID} I tried the ...
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### No-SQL Database Design for restaurant app

I've been working with SQL databases all my life and I am now trying to get into the NoSQL world. I am a looking for a piece of advice on whats the best practice in order to achieve this. Suppose I ...
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### One field with multiple values?

I know that what I'm asking can't be done or shouldn't be done, but I really don't know how to do it. This is the problem: 2 tables: - Drivers (id_driver, name, etc...) - Trucks (id_truck, model, ...
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### Applying normalization to a relational Database (Access & SQL Server)

This question is pretty specific but I hope it can get answered on here. There is a wide range of information about normalization but I feel what I have read so far isn't as effective as just stating ...
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### A question regarding the performance of normalization

I am sorry this is such a newb question, but it is one thing I am having a difficult time wrapping my mind around, and after an evening spent reading I finally just decided to ask for some ...
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### 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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### Fourth Normal Form

It's been about ten years since I paid real attention to fourth normal form, and my understanding of multi-value dependencies has seriously waned. How far is this table from 4NF and why? CREATE TABLE ...
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### What and How is the ID antipattern?

What is the ID antipattern and why / under which circumstances is it considered an antipattern? The id antipattern is having a unique ID column in each table. The ID is generated for each new ...
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### Closure set of functional dependency

Can anyone tell me what is the use of finding the closure set of a functional dependency? I know how to find F+ from F but don't know the use of F+.
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### DB Design: Looking for Performance improvement with a Column used in all SQL Queries

I recently got added to a new ASP .NET Project(A web application) .There were recent performance issues with the application, and I am in a team with their current task to Optimize some slow running ...
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### Building dependence between regional data (Street -> City -> PostalCode -> Country)

I'm in the process of designing a database to contain regional data to be used inside a CRM system. So, a user suspects that things like the city or country are automatically filled (or maybe just ...
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### Best way to create relationship between multiple tables

I have a question about how to best handle a table that would be shared among multiple relationships, but shouldn't really be joined with all these tables. For example, suppose I have a table that has ...
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### Is normalization advisable on transactional data?

I have read a lot of articles about normalized vs denormalized schemas, but I find very little mention of the cost of row insertion. I am considering the impact of converting a 100% denormalized ...
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### Users Characteristics

I'm really battling an issue where I have a Users table that has a growing number of user characteristics (regligion, smoking preferences, etc). The strategy I've used thus far has been to add a ...
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### How to break table into two without losing performance?

According to http://stackoverflow.com/a/174047/14731, splitting away infrequently-needed columns frees up the cache allowing faster retrieval of the commonly-used columns. I've got a table whose ...
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### Denormalization Strategies: When is it appropriate to create redundancy for faster querying?

So I sometimes see databases purposely add redundant information for faster querying. I saw that this was mentioned here but I was wondering when would this be better than indexing, or creating a ...
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### 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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### Is this SQL schema normalized according to 3NF?

This schema is for a sports statistics/data app Note: Pink background = string/char/varchar Yellow background = int/tinyint Green background = dateTime bold column = PRIMARY key id_* = FOREIGN ...
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### Creating a table with many optional fields

I am a developer (student) looking for some advice on what best approach should I follow while creating a table to model an entity that has a number of optional fields. There exists a need to model ...
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I am trying to make sense of an example of 3NF decomposition using the 4-step algorithm mentioned by Ullman here, but I'm not understanding what my lecturer is doing with the last step (or, worse, I'm ...
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### Move Commonly-Repeated Fields into a new Table

I'm still at the design stage for a new system, and I've noticed there are several places where different types of object share similar fields. In this case, we have customers, offices, warehouses ...
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### database normalization to 3NF [closed]

I am just at a complete lost. I need help with this. There should be 12 tables (or perhaps 11 since one table has just a single attribute) when you are finished with the normalization and merging of ...
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### How can I maintain old information after an update?

I am having an issue figuring out a solution to not lose old information. For example, customers can place many orders. Let's a customer, Mary, makes her 1st order in 2013. Fast-forward to 2014, ...
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### Normalise for a very small database?

I am designing a very small database (c. 250 rows). I have a number of datapoints for each record, which under normalization rules, ought to be in separate tables. For instance: Percentages of a ...
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### Trying to get BCNF out of this relation

The table is: Employee ( EID, Ename, PID, ProjectName, MID, ManagerName ) For the functional dependencies I got: EID==>(Ename) PID==>(ProjectName) ...
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### Database Normalization - Can one field point to another?

This may sound like a dumb question, but I am a software developer new to database design... So the concept makes sense to me, but maybe this doesn't carry-- Is it possible for a field in a record ...
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### Normalization of Time Series Data

I have a table containing various a/b test experiment performance on a daily basis. The table structure looks something like this: date | experiment | user_count | user_attr | sales ...
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### Database Normalization

If someone could guide me on helping me understand if my results are correct I would appreciate that. Let's say I have the following table: BOOK(BookTitle, AuthorName, BookType, ListPrice, ...
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### Photo caption and keyword associations

I am creating a database that references images. Keywords and captions will be part of the metadata. These captions and keywords are not necessarily added to the photos with the intent of facilitating ...
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### Transforming table to third normal form

I have a table like this: L(A, B, C, D, E) and functional dependencies are: AB -> CDE , C -> D, D-> B, D -> E. I need to transform this table into 3NF. I think it's not even in 2NF. I found 3 ...
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### Is this table in third normal form?

I have a table L(A, B, C). Functional dependencies are: A->B, A->C, B->A, B->C. Is this table in 3nf? My thoughts: A and B are keys of this table. Table is in 3nf if there are no transitive ...
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### Train Fare Database Normalisation

I have a database to normalize. The database has details of train ticket fares. The trains have different fares depending on the distance and I have to store these fares in the database It is not an ...
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### Users_With_Messages Table normal form

I have the following tables in my database: Above these tables (not pictured) is a Users table where the SendingUserId and ReceivingUserId are keyed onto (they are foreign keys). Are these tables ...
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### Does this break normalization?

I have an order table, and in the order table I have a contact_id. Now, each contact is linked to an account. For my order table, should I have both contact_id and account_id? If I wanted to say, ...
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### Normalization of irregular relations?

I have two tables in MySQL: The orders table CREATE TABLE `orders` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `transaction_id` varchar(20) COLLATE utf8_unicode_ci DEFAULT NULL, `task_id` ...
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### Decomposing table into BCNF that preserves dependencies

I have a relation like R(A,B,C) and dependencies like A->B , B->C , A->C I think the relation is in 2NF as candidate key is A. AFAIK when there is only one candidate key then the ...