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Questions tagged [3nf]

Third normal form (3NF) is a database design principle originally defined by E.F. Codd in 1971. It is built on the First normal form (1NF) and Second normal form(2NF). A relation R is in third normal form if it is in second normal form and every non-prime attribute of R is non-transitively dependent on each candidate key of R.

3NF is a normal form used in database normalization originally defined by E.F. Codd in 1971. It is built on top of First normal form (1NF) and Second normal form (2NF). A table is in 3NF if and only if for each of its functional dependencies X → Y, at least one of the following conditions holds:

  • X contains Y (that is, X → Y is trivial functional dependency), or
  • X is a superkey, or
  • every attribute in Y-X, the set difference between Y and X is a prime attribute is contained within a candidate key.

In other words it states that all non-key attributes should be determined by the candidate keys and not by any non-key attributes.

Normalization beyond 3NF

Most 3NF tables are free of update, insertion of deletion anomalies. Certain types of 3NF are affected by such anomalies. Some tables fail short of Boyce-Codd normal form (BCNF) or higher normal forms like 4NF, 5NF or 6NF.

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Third Normal Form uniqeness constraint

I am trying to make my database in 3NF i am confused about one thing. In the explanation below i do not understand how Zip can be the primary key of the address table if the zip can occur more than once. In the Student_Detail table a reoccuring…
Christopher
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Are my DB tables normalised to 3NF?

I need to make sure my schema is in 3NF, but am not too sure about my "StudentHomework Table" can someone help? http://prntscr.com/6ry22u
Apple Juice
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Understanding 3NF Concept

Hey I am working on an example problem where I have to identify which of this relations given are in 3NF/BCNF. These are the relations: R1(A,B,C,D,E) F=(CE->ABC, AB->C, C->A) R2(C,D,E,G) F=(CD->GE, E->D) Now according to the answers R1 is in 3NF…
user3467713
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Need guidance with making data conform with 3NF

I am currently working on a database assignment and for some reason I am struggling with this one basic question. Customer(cus_ID(underlined), name, address, mobile_phone) Please explain why these attributes are not in 3NF What would you do to the…
user3452356
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How can I normalize to 3NF these tables?

My tables are as follows : instructors(instructorID(PK), name, address, contact_details, pps_number, job_desc, specialty) admin(adminID(PK), name, address, contact_details, pps_number, job_desc) equipment(equipmentID(PK),…
user2978884
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Third Normal Form Assistance

I have the following: R = (A,B,C,D,E,F,G) FD = (A->B, C->D, E->F, ACE->G) I'm struggling with the decomposition into 3NF. I've read through several of the other posts and managed to confuse myself. Any assistance is greatly appreciated.
user2446307
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functional dependency

I am studying about functional dependency for sql and I got a question. We have functional dependencies A->B C->D CA->E D->F and I was trying to figure out whether that is decomposed relation or not For example we have two relationship First =…
Join Han
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How do I put this data into third normal form?

Here is my image of three entities, with ORDER and PRODUCT having many-to-many relationships: I understand that I have to remove transitive dependencies to turn it from 2NF to 3NF. Does this mean I need to create an associative table between ORDER…
nookingtons
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How to resolve dependencies that are both partial as well as transitive?

I have created this ER Diagram for a virtual car rental business. Each CAR can have many copies (CARCOPY) that can be hired many times over its lifetime. A CUSTOMER can hire more than one CARCOPY at once. I've created an entity named HIREDETAIL…
Luke Alanson
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Third normal form (3NF) explanation

Let some table stores information about subjects that are read by professors. The business rule is that one professor can read only one subject but the same subject can be read by many professor. Teacher field is unique. Id is a surrogate key. The…
PavelX
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Consider the universal relation R = {A, B, C, D, E, F, G, H, I, J}. What is the key for R?

Consider the universal relation R = {A, B, C, D, E, F, G, H, I, J}. What is the key for R? Decompose R into 2NF and then 3NF relations?
Ahsan Shabbir
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Is ther an relation with only one attribute is non-prime, and the relation at 2NF but not at 3NF?

Is ther an relation with only one attribute is non-prime (all other attribute are prime), and the relation at 2NF but not at 3NF?
avi n
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Is this database in third normal form/3NF?

I know this is probably a stupid question to some but I'm required to have this database in 3NF but know very little about normalisation as our teacher has not covered it. Could someone give me a simple yes or no answer as to whether it is in 3NF…
Shaun the Sheep
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When does BCNF not preserve functional dependencies, and should I then use 3NF?

When is BCNF not able to preserve functional dependencies? When is a 3NF decomposition desired instead of a BCNF decomposition preserving functional dependencies? Please explain with an example. I saw this question but it does not answer my…
Durgesh Singh
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Database Normalization Process to 3NF CustomerRental for CustNo, PropNo, OwnerNo, etc

I am trying to normalize the following table. I want to go from the UNF form to 3NF form. I want to know, what do you do at the 1NF stage? It says it's where you remove the repetitive columns or groups (ex. ManagerID, ManagerName). This is…
user2363682
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