Normalization
Defenition:Primarily a tool to validate and improve a logical design so that it satisfies certain constraints that avoid unnecessary duplication of data
simply to say ,it is just a way to process the relationship to avoid unnecessary duplication of data and produce well-structured relations.
Normalization process
first normal form
No multivalued attributes
Second Normal form
Then we should find the primary key: Sid ,Course_id
every non-key attribute must be depedent on by the entire key,not just part of the primary key
therefore it is not in the second normal form.
to convert this realtion into second normal form,we have to make all non-primary attributes to be fully functionally depedent on the primary key.To do that ,we need to decompose the two or more relations.
3-NF
2NF plus no transitive depedencies (one attribute functionally determines a second,which functionally determines a third)
when we are handling with the 2NF ,there maybe transitive depedency ,then we should make it into much smaller relation,docompose the relation,this is called the 3NF.
