primary-keydatabase-normalizationfunctional-dependencies3nf

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 info:

SID CID TID Grade
1 IS318 60192 A
1 IS301 45869 B
2 IS318 60192 A
3 IS318 60192 B
4 IS301 45869 A
4 IS318 60192 A

SID and CID, Composite primary key. SID,CID -> Grade and SID,TID -> Grade.

Is the table still in 3NF

Solution

  • Not as far as I understand it:

    A database relation (e.g. a database table) is said to meet third normal form standards if all the attributes (e.g. database columns) are functionally dependent on solely the primary key.

    https://en.wikipedia.org/wiki/Third_normal_form

    Since your attribute is not solely dependent on the primary key, then I think not.