2. Example 1
Album Tracks Artist ArtistCountry
Abby Road Here comes the
sun, Octopus
Garden,
Something, etc.
Beatles UK
Blond on Blond Rainy Day
Woman, Sad
eyed lady of
the lowlands,
Stuck in
Memphis with
the mobile blues
again
Bob Dylan US
3. This table could potentially fall prey to all three
anomalies. If the ArtistCountry was required,
it would be impossible to insert a new album if
you did not know the country of the artist. If
you deleted an album, you could accidently
remove all data about a given artist. Updating
tracks could be difficult and result in errors
because of the way they are listed in the cell.
4. Converting a spreadsheet into a relational
database is a common task for database
developers. The task is not as straightforward
as it might seem. Although you can often
import data from a spread-sheet directly into a
database management system, spreadsheets
are almost never well designed for relational
databases
5. First Normal Form
The First Normal Form [FN1] involves getting rid
of repeating groups or arrays. Each attribute
should contain only a single value of a single type.
This means a couple of things. For one, all the
values under an attribute should be about the
same thing. An attribute called ―Email,‖ for
instance, should contain emails only, no phone or
pager numbers. A second meaning is that each
value stored under an attribute should be a single
value, not an array or list of values. It would be
wrong, for example, to store two or three emails
for the same person separated by commas. An
entity is in First Normal Form if
6. An entity is in First Normal
Form if
Every attribute represents only one value.
There are no repeating groups or arrays.
Each row is unique.
7. This Album table does not meet the criteria for First
Normal Form. The main problem is in theTrack
column. The columnTrackcontains a list of songs
rather than a single value. This would make it very
difficult to locate information about any single song.
One solution that often occurs to novice database
developers is to enumerate a list of columns such as
Track1, Track2, Track3, and so on, to some arbitrary
number of tracks. This also violates the First Normal
Form by creating a repeating group. Say, for
argument’s sake, you made 13 track columns. What
happens to an album with fourteen tracks? What if an
album has only one or two tracks? Also consider what
you would need to do to find any individual track. You
would need to query 13 separate columns
8. Table in First Normal Form
AlbumTitle Track Artist ArtistCountr
y
Abby Road Here comes the sun Beatles UK
Abby Road Octopus’s Garden Beatles UK
Abby Road Something Beatles UK
Blond on Blond Rainy Day Woman Bob Dylan US
Blond on Blond Sad Eyed Lady of the lowlands Bob Dylan US
Blond on Blond Stuck in Mobile with the
Memphis
blues again
Bob Dylan US
First Normal Form is not sufficient. Every column contains a single value, and
there are no arrays or repeating groups, but there is a great deal of redundancy.
9. In the Album table, there are really at least two
large subjects. One is the Album itself. The
other is the Track.
The Artist information depends on the Track.
(Think about an album with tracks by multiple
artists.) To conform to the Second Normal
Form, the two functional dependencies—big
themes—must be broken into separate
entities.
10. To relate the Album entity to the Track entity, it
is necessary to create a primary key for the
Album entity that can be used to create a key–
foreign key relationship with the Track entity. It
is also a good idea to give the Track entity a
primary key. Here is what the tables look like
now:
AlbumKey AlbumTitle
ABRD Abby Road
BLBLB Blond On
Blond
11. TrackK
ey
Track AlbumKe
y
Artist ArtistCountr
y
HCTS Here comes the sun ABRD Beatles UK
OPGD Octopus’s Garden ABRD Beatles UK
SMTH Something ABRD Beatles UK
RDWM Rainy Day Woman BLBL Bob
Dylan
US
SELL Sad Eyed Lady of the
lowlands
BLBL Bob
Dylan
US
SMMB Stuck in Mobile with the
Memphis
blues again
BLBL Bob
Dylan
US
12. Third Normal Form
For an entity to be in Third Normal Form, it has to
first be in Second Normal Form. Third Normal
Form is about removing “transitive
dependencies.” A transitive dependency
describes an attribute that depends on another
attribute—not the primary key—for its eaning. The
idea is that every attribute should directly describe
the entity itself. If you have a Customer entity,
every attribute should describe the customer.
There shouldn’t be any attributes that describe
another attribute.
While transitive dependencies may seem trivial,
they do add to redundancy and therefore open the
possibilities for update and other anomalies.
13. There is a transitive dependency in the table.
ArtistCountry doesn’t describe the track; it
describes the Artist. The solution, as usual, is
to break out a separate table. Artist should be
its own entity.
AlbumKey AlbumTitle
ABRD Abby Road
BLBLB Blond On
Blond
ArtistKey ArtistName ArtistCount
ry
BTLS Beatles UK
BDLN Bob Dylan US
ArtistAlbum
14. Track-Table 3NF
Track
Key
Track Album
Key
Artist
Key
HCTS Here comes the
sun
ABRD BTLS
OPG
D
Octopus’s Garden ABRD BTLS
SMT
H
Something ABRD BTLS
RDW
M
Rainy Day
Woman
BLBL BDLN
SELL Sad Eyed Lady of
the lowlands
BLBL BDLN
SMM
B
Stuck in Mobile
with the Memphis
BLBL BDLN
