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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Normalization: Should I do this in 2NF or 3NF?
Consider a database storing the data of invoices, and each invoice takes the following form:
Invoice_Num: 1480
Handled By: John Keaton
Staff Num: 263
Staff Position: Trainee
Item_Num Item_Desc ...
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Way around Composite Primary Key requiring Composite Foreign Key
Here is a table called Make (where name is the PK)
name|other columns
----------------------
A | ...
B | ...
C | ...
And a table called Type (where make, name together is the PK and make ...
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0answers
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How to handle normalizing the concept of a grid, and also plan for data versioning?
I have inherited a database that has a normalized structure, except for its data tables which are aggressively denormalized. Our system mostly renders grids into a browser, and the previous developer ...
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663 views
Is a table without a primary key normalized?
In a lecture, my lecturer showed us a table without a primary key. Upon questioning, he said that in 3NF when you remove transitive dependencies it's ok to then have a table without a primary key.
...
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Its my class project about Normalization to 3NF. I need help in this project?
I just want to know the normalization I have done is correct or there any mistake? Please tell me.
enter image description here
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1answer
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Different categories of missings
Most database systems can represent missing values, typically as "Null" or something similar. But what if I want to represent different categories of missing data?
For categorical data, this is ...
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2answers
123 views
Is saving disk space still considered an advantage of normalization?
I have read a while back that one of the advantages of normalization is to save disk space (since normalization minimizes redundancy), but is saving disk space still considered an advantage of ...
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2answers
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A table with many null values VS many tables
Basically my level of DB knowledge enables me to create, select, delete and some simple things. When it comes to designing for performance, I have absolutely 0 knowledge.
So my question here is let ...
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1answer
41 views
Is a functional dependency on a “child” table allowed in third normal form (3NF)?
Consider two simple tables, OrderHeader and OrderDetail which contain, respectively, the data shown below:
OrderHeader
| OrderHeaderID | CustomerID | OrderTotal |
|---------------|------------|------...
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Can the Chase test algorithm only modify attributes on the right side of a functional dependency?
I'm attempting to apply the Chase Algorithm to determine if a decomposition is a lossless join decomposition.
Functional Dependencies = {A → C, B → D, C → D, DE → C, CE → A}
Here is my initial ...
2
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1answer
148 views
BCNF decomposition does not prevent insert anomaly?
I am in the process of designing a schema for a simple polling app and have tried to normalize it with the decomposition algorithm from this lecture.
Requirements
A poll has a unique id (poll_id), a ...
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1answer
139 views
Normalizing/combing mutliple tables with similar data
I'm working on setting up a database of vehicle records based on data from a third party vendor. There are 3 models: Vehicles, Transmissions, and Adaptors.
Both Vehicles and Transmissions are 1:n ...
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1answer
60 views
Primary key: (a) set it on a single column for two distinct data points or (b) set it on a combination of two columns, each for a separate data point?
I am designing a database for an e-commerce company. Each product will be identified by a unique ID (SKU). We want to format the SKU as LLLL000. LLLL is the parent product, for example Iphone X.
000 ...
2
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1answer
50 views
Can anyone help me understand the following paragraph?
I was reading Database Systems Design, Implementation and Management by Carlos Coronel. In the chapter of Normalization after he explained 3NF, he writes
The existence of multiple candidate keys ...
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1answer
113 views
MongoDB aggregation $unwind and 1NF
I have a basic rhetorical/theoretical question for people experienced using both MongoDB and RDBMS. Surprised SO has no Data Munging or Data Engineering forum.
In making an aggregation pipeline in ...
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0answers
52 views
Third Normal Form (3NF) Decomposition Scenario
I am trying to understand what are the steps to check if a decomposition of table is in 3NF.
There is a specific exercise I'm trying to solve with no success.
Given that R={A1,A2,A3,A4}
and F={A1→...
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1answer
53 views
Problem in testing normal form [closed]
In the question given in the link https://www.hackerrank.com/challenges/database-normalization-6/problem the answer is 2.
But I cannot understand why all the relations are not in BCNF (Since for all ...
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1answer
70 views
For BCNF decomposition, is it okay to have a relation with none of the original functional dependencies?
Given the relation R[c, f, g, h, e, j, a, b, d, i] with the below functional dependencies I have come up with the below solution. However, I am unsure about it, considering R8 has none of the listed ...
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1answer
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Is this a good database design or transition? Normalize to Denormalized for Data Warehousing [closed]
As of now in sql server , we have a data and a series normalized table structure that is connected to a C# web app (Human Resource / Recruiting System) (slightly medium (or small 12,000 rows.) size ...
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1answer
59 views
Using NULL values for foreign key with normalization
I am creating a table as follows:
Building (PK: buildingID)
Area (PK: areaID, FK: buildingID)
Room (PK: roomID, FK: buildingID, FK: areaID)
All rooms are in a building. Some rooms can be in an area ...
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0answers
50 views
Setting up a Grand Jury relational database structure
I'm designing a database to store information about a grand jury. I'm wondering if my tables are normalized, and if they structure makes sense.
A report is sent in for review by grand jury.
Then a ...
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1answer
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Keeping reference in an array format
I have a design with an orders table and products table. Each order can have many products, so 1 order N products.
The default design would be to have something like this:
orders table
order_id, ...
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2answers
79 views
Modeling Sellers and Products
I'm trying to model product and seller information. The seller can be either an individual, or a company, or a company with branches (and the product is being sold by a particular branch). Each ...
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1answer
29 views
Are these relations in BCNF?
I have a homework question that I am trying to understand but having a tough time with this question. Any explanation or even pointers would be very appreciated (no exact answer expected - I am trying ...
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1answer
28 views
How to reconstruct functional dependencies from 3NF decomposition?
I have the following decomposition for the relation R(A,B,C,D):
R1 = (A,B),
R2 = (B,C),
R3 = (A,D).
It is given that AD is the only candidate key for the original relation and that R is not in BCNF. ...
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0answers
45 views
Surrogate foreign keys allow inconsistent data - which normal form does this violate?
We have inherited a system which has surrogate keys on every table (that is, an auto-increment primary key, id). All of the foreign key constraints are on individual surrogate keys, and this seems to ...
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0answers
136 views
How to check if functional dependencies are preserved?
I have the following functional dependencies for the schema R=(a,b,c,d,e,g):
{b→c, dg→ce, bc→dg, e→a, g→bd}.
I want to decompose R into two schema's: R1=(a,b,c,e) and R2=(b,d,g) and make sure the ...
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1answer
110 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 ...
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1answer
123 views
How to find minimal cover when attributes have equal chance to be not necessary?
I have the schema which consists of 6 attributes: t,s,r,w,e,g.
For the schema I have the following functional dependencies:
s,w --> r;t,w,g --> r,e;s,r --> t,g; e -->w; g --> t,s;r,w,...
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2answers
62 views
Normalizing the Test Table
I'm a web developer looking to leverage more of the power of my RDBMS. I'm currently learning about normalization of data and database design.
In the book that I am reading, we started off with one ...
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How to abstract duplicate data to separate table? A stab at normalization
New to PostgreSQL.
I have a table like so called "books."
Modify id isbn title author year
edit 2 380795272 Krondor: The Betrayal Feist 1998
edit 3 ...
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1answer
147 views
Is sql_variant compatible with First Normal Form (1NF)?
1NF rule says that we should not keep data of different types in one single column. Does it mean that sql_variant is not compatible with first normal form hence should not be used?
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2answers
39 views
Normalizing data past initial db design phase
I wanted to poke at everyones brain to better understand when it makes sense to normalize a table that carries redundant data. I recently worked on a project at my startup and really question myself ...
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1answer
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Designing a join table for max n records
I know that a basic rule for designing a relational dataset is to not do things like this:
create table Order (
OrderID int indentity(1, 1) not null, -- PK
CustomerID int identity(1, 1) not ...
2
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1answer
56 views
Questions Concerning the Chase Test
For the question above, my work for each of the questions is below the concerns. Here are my main concerns:
Does the order in which you use the relations matter?
Can you end up with less tuples with ...
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1answer
35 views
Question concerning minimal/cannonical cover
For the question above, I am confused with how to approach simplifying the left hand side of BDCE->A. Do I get rid of E, as D depends on it, or do I get rid of CD as well, as CD->A?
Here's what I ...
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3answers
217 views
What normalization rules does this table break
Our previous DBA got fed up with the development teams frequent requests to change the database schema to add and delete columns. He then advised to the developers that he would create simple tables ...
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0answers
35 views
Decomposition to 3NF
I need the help with following question as part of my assignment / homework
Provided the following structure
CLASS(Reg-NO ,Unit-ID,UnitTitle,Lecturer,Office)
The following functional dependencies ...
2
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1answer
38 views
Name for a “lookup” table with values in separate rows
I am looking to put a name on a particular situation. When you remove a comma-delimited column and split it into separate rows in a new table, what is that type of table called?
In the example below,...
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0answers
56 views
Normalizing a relation schema with 'abstract' attribute names
I'm a student currently attending a database design course and I'm having some issues normalizing 'abstract' attribute relation schemas from 1NF all the way to 3NF.
When we used examples with '...
3
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1answer
74 views
Decomposition in 3NF using synthesis
I have an assignment at the university and it is about decomposition. These are the relation and FDs.
V={ABCDEF},F={AB→CD,ABDE→F,BC→A,C→DF}
We need to find candidate keys, canonical cover(basis) and ...
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1answer
50 views
3NF Normalization Problem Employing an Algorithm
I'm getting stucked in figuring out how to obtain the third normal form (3NF) using an algorithm ( removing attributes and then functional dependencies ).
The relation R( A,B,C,D,E,F,G,H,I,J,K ) has ...
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3answers
326 views
How to transfer data from denormalized table to normalized tables in Oracle?
Hi I currently have a database set up with a table like this:
Grades: student name|class name|overall|hw|test|quiz|project|val
where student name and class name are type varchar2 with the rest being ...
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1answer
73 views
How to prevent null foreign key during database normalization?
I'm rather new to databases and am having a hard time trying to figure out how to structure my database. This database contains students, classes and all their grades both overall and in categories (...
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1answer
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Is it Important to Understand Each Normal Form?
I have been studying database design and programming for quite some time now, but I still can't get a grasp of understanding each individual normal form (that is, 1NF, 2NF and 3NF).
Seeing as anytime ...
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3answers
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Normalization Problem for drugstores information [closed]
I want to capture all data about 10000 drug stores in my country.
I design as follows:
Drugstore main info (uniqueid, hi_number, drugstorename, drugstoretype, drugstorerelateuniversity, servicetype, ...
2
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1answer
62 views
Assessing the normal form for a relation with a multi-valued attribute
Assume that you have designed the following schema of relations:
COURSES (CID, CNAME)
STUDENTS(SID, SNAME, FAV_CIDS)
However, you can not have a relation with set valued attributes (Did not really ...
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1answer
188 views
Attempt to find Transitive Dependencies
Table From this table example I am trying to understand both this dependencies. According to me partial dependencies have a primary composite key and transitive dont have.
I try to figure out Partial ...
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3answers
167 views
When is it beneficial to move duplicate data to a reference table?
If there is column with values from some finite set S, for example S = { alive, dead, unknown } for a life_state column in a persons table, when is it beneficial to add a reference table?
Options:
...
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1answer
49 views
Now to normalize table when position in group uniquely identifies entity
I need to model charts such as the one displayed below...
... and came up with the following:
For the sample chart I originally showed..
charts.name is "Custom transactions", charts.y_legend is "...
