Database Functional Dependencies And Relational Algebra

[iGuest 3]

Can anyone really define the term functional dependency for me in database systems and also i need help in normalisation , how to carry out all the normal forms on a given relation

[Ananya 0]

Functional dependency determines the relationship between attributes of a table.If say suppose a table has attributes like student_id, course_id ,course,teacher,address.Now student_id determines address of the student and the courses chosen by him.Course_id determines course.So this can be shown as student_id->course,address and course_id->course,teacher.So these 2 are functional dependencies for the above table.so now since all the attributes are not being determined by only one attribute so Primary keys for this table will be student_id,course_id.Normal forms are categorized as 1NF,2NF,3NF,BCNF.1NF is just to check check that no repeating groups of data are there.The table now formed has got 5 attributes but some of the non-key attributes are being determined by only one of the 2 keys.Here non key attributes are course,teacher,address.So this table needs to be broken into 2 tables so that this partial dependency doesn't exist.This breaking up of base table into sub tables is Normalization and removal of partial dependency is done in 2NF.So now 2 tables are- (student_id,course,address),(course_id,course,teacher).