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Questions tagged [normalization]

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 Design for Maintaining Supplier Invoice

I am not sure whether it is right to ask such question here. However, It comes to my mind this would be the best place to start. My needs are quite simple. As a distributor, I want to maintain all ...
0 votes
1 answer
630 views

Database Model for Various Type of Sensors

I am planning to build a database that will store sensor value for various type of sensors in a factory building. Is there any best practice on how to do this? - Option 1 : should I integrate all ...
-1 votes
0 answers
47 views

How to understand that a database design is in 3rd Normal Form?

Database design: Education plan: ED_ID, Subject (text), Specialty_ID (int), Teacher_ID (int), Group_ID (int), Plan (number of hours) (int), Fact (number of hours) (int), Control form (text), Semester (...
-1 votes
1 answer
42 views

Customer Address Design Probelm

I'm designing a database for E-commercial. So the Customer have many address also 1 address also has many customers owned so I have another CustomerAddress table (many-to-many relation). Here detail : ...
-1 votes
2 answers
3k views

How can I design address table?

Hello I need designing addresses table. I designed it but I didn't like it very much. My needs: I have customers and users (admins). I have addresses for customers and users. We need design in ...
1 vote
2 answers
1k views

How to solve multiple minimal covers for functional dependencies?

I have the schema: a,b,c,d,e,g and the following functional dependencies: b->c, dg->ce, bc->dg, e->a, g->bd for which I want to find the minimal cover. It seems that more than one ...
-1 votes
1 answer
93 views

Create a category column or a table for each category?

Which is better? Table: Words Columns: ID, Word, ParentWordID, CatID Table: Categories Columns: CatID, Category Or: Table: Words Columns: ID, Word Table: Categories Columns: CatID, Categories ...
1 vote
1 answer
1k views

Finding all possible minimal covers

I have a relation schema R = {A, B, C} and the following functional dependencies: A → B A → C B → A B → C C → A C → B How many different minimal covers can I derive from this relation schema? I have ...
0 votes
1 answer
920 views

How do foreign keys affect partial and transitive dependencies (databases)

I'm struggling to work out how foreign keys can affect partial and transitive dependencies when normalising databases. I have multiple tables, two of which are job offer and accepted job. in job offer,...
0 votes
1 answer
74 views

3NF Decomposition and NP-Completeness

I have a question about the computational complexity of the algorithm that allows us to decompose a schema into 3NF. My book says that the decisional problem of telling if a schema complies with the ...
-1 votes
1 answer
53 views

Should we repeat multilevel dependency reference columns to avoid multiple joins breaking the normal forms for better performance

In general I know repeating information in tables are not considered a good database design But I have a question for following particular design for multi level parent child relationship ...
0 votes
2 answers
62 views

3NF normalized table design

I am struggling with how to normalize a database where there is multiple addresses pr. user. The situation is that a user can have both a regular address and a delivery address. When a user make an ...
6 votes
2 answers
24k views

How does normalization fix the three types of update anomalies?

I have been reading 'Database Systems: A practical approach to design, implementation and management' by Connolly and Begg in order to understand database normalization (chapter 14). The three DB ...
7 votes
3 answers
8k views

When to apply normalization in database design

Prior to learning about normalization I would usually read the scenario/description in the requirements and draw up an ER diagram (using Chen's notation) using nouns as entities and verbs as clues to ...
1 vote
1 answer
454 views

ERD directly producing 5NF relational schema - is this desirable?

I have been given a case study of Event Management. I have to develop an entity-relationship diagram (ERD), and based on it check if the resulting relational schema meets the different normal forms. I ...
4 votes
2 answers
95 views

how can this table is in all three normal forms have update anomalies?

Imagine a database with one table about dancing. Names of different people can be identical, but we assume no people have the same name and the same birthdate. The same pair of dancers can dance ...
0 votes
1 answer
52 views

Why do these examples not in 5NF exhibit update problems?

The tables below (Fig 17.20) were extracted from the book 'An Introduction to Database Systems' by C. S. Date, v. 1 -Longman Higher Education (1985) 4th edition. I don't understand the need for ...
2 votes
1 answer
129 views

Which is the best way to model different types of people and relationships in a database?

I have a scenario where I have two tables, person_natural and person_legal. Case 1: I have employees, farmers, customers, and suppliers. Should I have an enum in each table (person_natural or ...
0 votes
2 answers
85 views

Handling two different types of relationships between same two tables

I'm working on a database where I have two tables where there can be different types of relationships between them, and I'm struggling with the best way to handle it because all the options I seem to ...
2 votes
3 answers
5k views

3NF Vs 2NF, which is more strict?

Which of these is true: If a table is in 2nd normal-form then it must be in 3rd normal-form. If a table is in 3rd normal-form then it must be in 2nd normal-form. I know only one of them is correct, ...
1 vote
1 answer
45 views

Why is the following decomposition into 2NF wrong?

Consider the relation R(A, B, C, D, E), with the functional dependencies being {BE->A, D->E}. What is R's decomposition in 2NF? The answer is R1(D, E); R2(B, E, A); R3(B, C, D) I've derived that ...
0 votes
1 answer
93 views

Database design, one to one relation split into multiple tables

Let's assume we have following database: Or in pseudo sql format (all columns are not null): create table road ( id int PK ) create table item_on_road ( id int PK road_id int FK road.id ...
1 vote
2 answers
69 views

Correct (as in normalized) way to express a relationship between 3 tables with complex(?) constraints?

I'll be using Postgres for the examples, but feel free to show examples in other databases if needed. The simplified schema: create table factory ( id serial primary key, detail text not null ); ...
0 votes
0 answers
45 views

what violates the first normalization rule

I was convinced that what violated the first normation rule was having a multivalued column. id name friends 1 'john' 'Maycon, Gabriel' That has multiple names in the same column. Compound ...
9 votes
2 answers
1k views

How can I losslessly decompose this table?

I have a table with the following PK (primary key): child_id integer parent_id integer date datetime child_id and parent_id are FKs (foreign keys) to entity tables. The child table also ...
-1 votes
1 answer
155 views

how to normalize to 3NF, for example this table about employees, roles, projects and assignments

I'm studying database administration and data modelling as a part of my ICT Apprenticeship course in a Web Development team. I understand the concept of eliminating redundant data, stopping anomalies ...
-1 votes
1 answer
335 views

Choosing Primary & Foreign Keys & normalizing Person, Name, DOB & Wedding tables

I am in the conceptual design of a database, building tables and views, selecting the PKs and FKs (primary and foreign keys) and normalizing. Unfortunately, I am constrained to use Power Pivot on ...
-1 votes
1 answer
15 views

How to map question to chapters in a examination system?

I am going to create an multiple choice based examination system. I am new to database design and want your help to answer a few questions. How to model questions and questions category? Context: ...
2 votes
2 answers
11k views

Database Design for Airline Reservation System

I'm creating a very simple database system for an airline company, for learning purposes. Flight, passenger and payment are my entities and I've used relational format for the relationships between ...
-1 votes
1 answer
36 views

What normalization rules flattening one-to-many violate?

I'm trying to better understand NF in a theoretical sense. The data I have feels wrong but I'm not sure if/how it violates normalization Example table: product inc_charger inc_cable inc_headphones A ...
6 votes
8 answers
44k views

What is Atomic Relation in First Normal Form

I have read the definition of 1NF which is, "If each attribute of relation is atomic". Please tell me what is Atomic.
0 votes
0 answers
26 views

Design for massive dimensional table to improve query time? Can it be partitioned horizontally?

I've never had this issue before -- but inheriting a big data project. There is a dimensional table "account" or "user" that contains every dimensions known to mankind. Or let's ...
0 votes
1 answer
76 views

Database design - normalisation query

I am a teacher and am querying a solution given by our examination board. The question is shown below and I'd like to ask for help in understanding why my solution would not be acceptable. Here's the ...
-1 votes
1 answer
42 views

Design and normalization issue : type of FK depends of an other field

I have a CapitalIncrease table, which contains a list of available payment methods. For each payment method, I need to put some data (SepaDocument OR Iban OR Crypto). Here is a mermaidjs graphic of ...
0 votes
1 answer
34 views

Are functional depencies with boolean conditions a thing?

Suppose we have a relation R(A, B, C) with the FD A -> B. Let's say that, for two tuples t and u in R, if both t[C] and u[C] satisfy a boolean condition - say less than a constant C - then t[B] = u[...
3 votes
0 answers
79 views

Best practices for heavily coded data in a relational database and lookup tables

I'm working on converting a legacy system into a more modern web application and I keep finding myself tripping over normalizing the data. The dataset is quite large; about 30 tables with around 15 ...
0 votes
1 answer
61 views

Normalisation with an Underlying Hierarchy

I'm designing a new database schema, and every time I do, I like to check my assumptions on normalisation. Something I haven't been able to find a definitive answer for here or by searching the web is ...
-2 votes
2 answers
90 views

Why is it a bad idea to have multiple values in a column in a relational database?

One problem I've found is slow database queries. If I had a table that had a column titled customer and another column titled grocery_items that contained multiple grocery items, then a simple query ...
1 vote
1 answer
1k views

Advantages and disadvantages of normalisation

Briefly, what are the main advantages and disadvantages of normalisation as a technique for database design? It may be easier to answer this with a snapshot of some unorganised data, as a concrete ...
0 votes
1 answer
71 views

Overkill or good application of normalization to create parent table just to associate a collection of children

I have a situation where I need to keep a group of detail rows together but where the "parent" has no additional attributes and the "children" have no purpose on their own. I ...
0 votes
0 answers
55 views

Functional Dependencies and Armstrong notation fundementals [duplicate]

if AB -> C and B -> A does that mean B -> C? B -> B is trivial and if we do composition with B->A, it becomes (B-> BA), then by transitivity does that mean B->C? but if B -> C ...
-1 votes
2 answers
170 views

If `AB->C` and `A->B` , `A->C`?

I'm new to databases, is this true? if so, how can we deduce that? I don't know how to use the properties to get an answer, could you help>
0 votes
1 answer
179 views

Design database table for property listing

I want to design a database for a listing website, this is the first time I design the database, so I am not sure if I in the correct path. Here is the fields that needed in a listing, title - ...
0 votes
1 answer
510 views

Correct entity relationship diagram representation of a normalized table with a NOT NULL foreign key

Intro Hi everyone, this is mainly a classification/theoretical question on the topic of inheritance and normalization techniques in database design and their appropriate representation in entity ...
0 votes
1 answer
421 views

How to create a trigger that generate a random specific output to insert into a table in MariaDB?

I have an account table which is laid out in 3NF: CREATE TABLE account ( account_id INT AUTO_INCREMENT, customer_id INT NOT NULL, account_type_id VARCHAR(15) NOT NULL, is_active ...
1 vote
3 answers
1k views

How can I design Person table in MySQL?

I have two person type: Users and Clients. Users can login the panel but clients can't login the panel. My current database: (but this design not good for me. I need to connect these tables to the ...
1 vote
4 answers
112 views

deciding what/how many tables to use; normalisation suggests one

I am using Oracle Database 18c Express Edition with SQL Developer. I have been asked to build a database to log sales in a shop: Date Day Time Value [either Low, Medium, or High] Location [on a (-5,-...
3 votes
2 answers
2k views

Why is this relation in 3NF?

I have a relation: R4 = {{T,U,V}, {T → U, U → T, T → V}} I know from looking at the answer key that this relation is in BCNF. I'm going through the process of rigorously determining what normal ...
1 vote
1 answer
744 views

Is this design in 3NF? Why to choose another design not in 3NF

I have entities Objects, Parts, Subparts and Items and the following restrictions: A Part belongs to one and only one Object. A Subpart belongs to one and only one Part. An Item belongs to one and ...
3 votes
1 answer
31k views

Decomposition of a relation to 2NF then to 3NF

I am having trouble decomposing a relation with given functional dependencies into 2NF then 3NF. For example: Relation R has attribute set {A, B, C, D, E, F, G, H, I, J}` and functional dependency ...

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