Re: Sixth normal form

On 30 jul, 12:45, Sameeksha <sameeksha.ch...@xxxxxxxxx> wrote:
Googling out for definition and explanation for sixth normal form only
resulted in the following information - "6th normal form states that a
relation R should not contain any non-trivial join dependencies". Also
everywhere it is stated that this normal form takes into account the
temporal (time) dimension to the relational model, and that current
implementations like SQL server 2005 do not implement this normal
form.

It would help if you first explained what you already know, so we
don't spend time on explaining what you already know. Do you know what
at join dependency is? Do you know when it is trivial?

Btw. where and in what context did you read that SQL server did not
support this normal form? That is a rather odd statement since the
normal form is just about how much to split your relations into
projections, so strictly speaking it needs no support at all form the
DBMS. But perhaps support for temporal features was meant?

Any more explanation and preferably an example would help in
understanding the concept behind this normal form.

Informally put it says that every distinct fact gets its own relation
or "if you can split, then you should". So if you have a relation
Student(student_id, name, address) then the fact that the student with
a certain id has a certain name is split form the fact the this
student lives at a certain address. This is different from 5NF since
there you only split when there is a risk of redundancy or update
anomalies.

-- Jan Hidders

.

Relevant Pages

  • Re: Sixth normal form
    ... relation R should not contain any non-trivial join dependencies". ... everywhere it is stated that this normal form takes into account the ... so strictly speaking it needs no support at all form the ... absolutely necessary, for example, to support a temporal dimension. ...
    (comp.databases.theory)
  • Re: Sixth normal form
    ... relation R should not contain any non-trivial join dependencies". ... everywhere it is stated that this normal form takes into account the ... example - a table contains TeacherId, SkillId and CourseId as fields. ...
    (comp.databases.theory)
  • Re: Sixth normal form
    ... relation R should not contain any non-trivial join dependencies". ... everywhere it is stated that this normal form takes into account the ... so strictly speaking it needs no support at all form the ... absolutely necessary, for example, to support a temporal dimension. ...
    (comp.databases.theory)
  • Re: Sixth normal form
    ... relation R should not contain any non-trivial join dependencies". ... everywhere it is stated that this normal form takes into account the ... The join dependency definition is the definition for 5th normal form. ...
    (comp.databases.theory)