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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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A non prime attribute depends on composition of a partial Partial primary key and a non prime attribute. Is the table still considered to be in 3NF

Here is the table descriptions: Students SID SNAME 1 Adams 2 Jones 3 Smith 4 Baker Teachers TID TNAME 60192 Howser 45869 Langley Classes CID CNAME IS318 Database IS301 Java Student…
Shanmukha Reddy
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Is this database 3NF or BCNF?

I have this table that the rules are: A student is examined in a discipline and obtains a position on the class list. It is known that two students cannot obtain the same position in the same subject. Is this a 3NF database or BCNF, i cant have a…
Young JooJ
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3NF Normalization and Decomposition

I am currently in a DB class and working through Normalization, and am running into some trouble. Am hoping I can get some assistance working through this. I have searched for the last 30 min and haven't found anything that helps solve my question,…
Tommy O'Connell
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Have I normalized this database to a 3NF level the right way?

I had a lecture at college recently about normalizing databases, but since we are online I can't really ask a lot of questions, so here I am. Can someone tell me if I'm doing the conversion right, if not where am I mistaking? The Task: My…
Borislav
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Normalization Form

would like to ask a question that related with normalization form. R = A,B,C,D AB -> CD CD -> AB Is this is 3NF with BCNF ? why ?
Yannis
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is this in 3NF?

is this in 3NF? mysql show tables; +--------------------+ | Tables_in_hospital | +--------------------+ | address | | bed | | department | | hospital_number | | phone_number | | region | | type …
dsa02084
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Normalization generates a table with no clear purpose

Overview I have an assignment regarding database modelling in which I have to model a database for a shop. When normalizing from 0NF to 3NF, I end up with a table whose attributes do not seem to be related. NOTE For brevity, I removed most of the…
Isfaaq
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3NF Normalization tables from Domain Model

Hoping to get some assistance on how this would be represented in a database table (3rd normal form). I feel what I have done is incorrect. I understand that with a one to many association, the primary key from the "1" table (in this instance…
LukeJ
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Is the following table in 3NF?

I have the following table: criteria -> (ID,COURSE,REIMBURSEMENTAMOUNT) The REIMBURSEMENTAMOUNT attribute reflects the percent of the course cost that is reimbursed. I am afraid that this table is not in 3NF because the course depends on the ID and…
dan
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Third Normal Form of a Users table with user ID and username columns

I've been learning about database Normalisation, and I have a question regarding a users table I have for my web app. The table schema is as follows: users (user_id, username, password, first_name, last_name, ver_code, verified) I want to know if…
user5526660
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Normalization. Looking for feedback on what should be 3NF

I am creating a database for a super market in my database class. The database needs to be at least 3nf but if possible, BCNF. Could someone let me know if this is satisfactory? I believe it is and I just want to make sure.
Sean Gallagher
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Prime attribute and keys

Is a prime attribute only a member of candidate keys or can it also be superkeys? I am a bit confused as I am reading somewhere that a prime attribute can be a member of ANY key, and other says it needs to be a member of a Candidate key.
user7722505
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Which of the following are true regarding 3NF and BCNF?

Suppose i have a table A which consists of only 1 candidate key then what is true ? If it is in 3NF, then it is also in BCNF or not ?
Garrick
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How can I make this relation into the third normal form (3NF)?

I want to normalise this table and so far I managed to get it up to 2NF but I'm very confused on how I can possibly make it a 3NF. Primary keys in bold. 1NF: Appointment (StaffNo, DName, PatName, PatNum, PatTelNo, ApptDateTime, RoomNo,…
Gautam Nath
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The right way to normalize database into 3NF

I have this database: R(A, B, C, D, E) Keys: A F = {A -> B, D -> E, C -> D} I normalize it into 3NF like this: R(A, B, C, D, E) Keys: AD F = {AD -> B, AD -> E, C -> D} What I do is when I check D -> E, D is not a superkey and E is not a key…
user4754843
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