In this case, there is only one: I guess it was so obvious to me that this was a useless field I thought it would be just as obvious to everyone and since either way we got rid of the field, what did it matter? We need to know the student, the subject and the exam being taken.
So we may safely get rid of the SubjectName field altogether without sacrificing any integrity of the model. This will increase the computational time. What is the absolute minimum information do we need to uniquely identify the grade?
This process will mainly divide large tables in to smaller tables with fewer redundancies. Fine, this is one of the candidate keys.
Decomposition of tables will result in additional join operations or Cartesian products when executing queries. But I do remember I had a prof who, after 2nf authentication better than 1nf teaching us the proper meaning of "functional dependency" and "non-prime attribute" and all the other buzzwords, gave us a series of simple questions to ask to see if a particular normal form was reached.
SubjectName is dependent only on SubjectCode -- a subset of the candidate key. However, at one point I said "this tuple is not in 2nf," which more properly should have been, "this entity is not in 2nf. If we ask the question of an attribute and the answer is not all or part of the candidate key, then the tuple is not in 3nf.
For a table to comply with 2NF, it should be complied with 1NF and any attribute that is not a part of any candidate key i.
These smaller tables will be related to each other through well defined relationships. So this tuple is not in 2nf.
Similarly, obtaining a table that complies with the 2NF will require decomposing a table that is in the 1NF. This would match the second candidate key. As the supplied tuple seems to be the definition of an entity called "grade", then we can normalize it.
Therefore in general, obtaining a table that complies with the 3NF form will require decomposing a table that is in the 2NF.
Codd, who is also the inventor of the relational model and the concept of normalization. One unique reference to a row in the Subjects table is quite enough. Assuming that SubjectCode and SubjectName are both candidate keys for the Subject entity, there is no reason to have both these fields here.
In Carlo Zaniolo produced a differently expressed definition for 3NF. A table that complies with 1NF assures that it actually represents a relation i. However, if a table that complies with 1NF contains candidate keys that are only made up of a single attribute i.
Remove it from this tuple and it is now in 2nf.
On the other hand, the tables that comply with stronger normal forms would have fewer redundancies than tables that only comply with weaker normal forms.
Tables that comply with the 3NF generally do not contain anomalies that occur when inserting, deleting or updating records in the table. In a well normalized database, any alteration or modification in data will requires modifying only a single table.
However, in my original answer, in my desire to show another level of normalization, I ignored that SubjectName had been used in a candidate key and considered it just another non-prime attribute. V V V But the answer could just as well have been student name, subject name and exam.
One important property is that a table that comply with 1NF could not contain any attributes that are relational valued i. SubjectCode should be the primary key of a Subjects table so that is the proper location to place SubjectName.1NF, 2NF, and 3NF are _____.
normalization stages. From a structural point of view, 2NF is better than _____. 1NF. Normalization works through a series of stages called normal forms. For most purposes in business database design, _____ stages are as high as you need to go in the normalization process.
Normalisation Forms • 1NF • 2NF (better than 1NF) • 3NF (better than 2NF; most of the time as high as needed for businesses databases) • Boyce-Codd NF • 4NF Pitfalls of Normalisation A higher normalisation level is not necessarily the best.
Explaining 2NF vs 3NF with an example. up vote 12 down vote favorite. 1. I have a problem with second normal form (2NF) and I have been unable to solve it by using Google. It is making me crazy because I am a teacher and I don't want to teach wrong stuff to my students.
Normalisation - 2NF vs 3NF. Ask Question. I know we say 2NF is "the whole key" and 3NF "nothing but the key". Referencing this great answer by Smashery: What are 1NF, 2NF and 3NF in database design? The more normalized the better for data but not for performance nor understanding if it gets really too complicated.
1NF, 2NF and 3NF are normal forms that are used in relational databases to minimize redundancies in tables. 3NF is considered as a stronger normal form than the 2NF, and it is considered as a stronger normal form than 1NF.
2nf Authentication Better Than 1nf Essay Is two factor authentication better than one-factor authentication? Critically appraise this using concept of security goals and implementation. OP- 10% orAssignment- 15% The impact of the internet over the last few years has meant fundamental changes in the way we access the information.Download