Normalisering

Der er 5 NF og BCNF (Boyce Codd NF) og
DKNF (Domain Key NF).

1-3 er ret almindelige hvis du laver data
modeller til \'business\' BCNF er et special
tilfælde af 3.NF, der ofte bliver opfyldt,
uden \'at man ved\' det. En lang række tabeller
(eller relationer) er på BCNF når de er på
3.NF.
De sidste 3 er 4,5NF og DKNF(Domain Key NF). De er måske lidt mere eksotiske. Jeg har prøvet at normalisere efter dem, og da jeg var færdig denormaliserede
jeg dem tilbage på BCNF, for at få en rimelig
ydelse. Hvis du er ude efter mere dybde kan du
prøve:

http://csc.noctrl.edu/f/kwt/460/normal.htm

det er også et meget svært spørgsmå at give et svar på via eksperten, men jeg kan forstå din situation, så måske vi kan finde på noget. Ser du jeg har nogle sider om emnet på engelsk (men det gør vel ikke noget). Har du ICQ ???

fra (og nogen gang med) NF3 bliver de minder og mindre nyttige.

se: http://www.gslis.utexas.edu/~l384k11w/normover.html

Formal Definitions of the Normal Forms

1st Normal Form (1NF)

Def: A table (relation) is in 1NF if

    1. There are no duplicated rows in the table.

    2. Each cell is single-valued (i.e., there are no repeating groups or arrays).

    3. Entries in a column (attribute, field) are of the same kind.

Note: The order of the rows is immaterial; the order of the columns is immaterial.

Note: The requirement that there be no duplicated rows in the table means that the table has a key (although the key
might be made up of more than one column--even, possibly, of all the columns).

2nd Normal Form (2NF)

Def: A table is in 2NF if it is in 1NF and if all non-key attributes are dependent on all of the key.

Note: Since a partial dependency occurs when a non-key attribute is dependent on only a part of the (composite) key,
the definition of 2NF is sometimes phrased as, \"A table is in 2NF if it is in 1NF and if it has no partial dependencies.\"

3rd Normal Form (3NF)

Def: A table is in 3NF if it is in 2NF and if it has no transitive dependencies.

Boyce-Codd Normal Form (BCNF)

Def: A table is in BCNF if it is in 3NF and if every determinant is a candidate key.

4th Normal Form (4NF)

Def: A table is in 4NF if it is in BCNF and if it has no multi-valued dependencies.

5th Normal Form (5NF)

Def: A table is in 5NF, also called \"Projection-Join Normal Form\" (PJNF), if it is in 4NF and if every join
dependency in the table is a consequence of the candidate keys of the table.

Domain-Key Normal Form (DKNF)

Def: A table is in DKNF if every constraint on the table is a logical consequence of the definition of keys and
domains.

oki :-) de noter jeg har om emnet er ikke meget bedre en det jakoba linker til. Ville ellers have tilbudt at tage et copi og sende til dig :-)

sorry det har taget så lang tid
EKSAMENS stress, og så fik jeg
desværre ikke brug for de smarte
ting om normalisering.

points go to cli, men jeg ved ikke
rigtig hvordan, for du står ikke i
listen?

jamen jeg vil da gerne have point :)