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Normalisation
FIRST NORMAL FORM
1NF
2NF
3NF
BCNF
DEFINITION: A table is in its first normal form if it
contains no repeating attributes or groups of
attributes.
NON-KEY
KEY
NON-KEY
KEY
KEY

 NON-KEY
 NON-KEY

KEY

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STUDENT(Number, Name, Classes)
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V
STUDENT(Number, Name, Classes)
SECOND NORMAL FORM
CODD’S TWELVE RULES FOR
RELATIONAL DATABASES
1.
Data should be presented to the user in table form.
2.
Every data element should be accessible without
ambiguity.
3.
A field should be allowed to remain empty for future
use.
4.
The description of a database should be accessible to the
user.
5.
A database must support a clearly defined language to
define the database, view the definition, manipulate the
data, and restrict some data values to maintain integrity.
6.
Data should be able to be changed through any view
available to the user.
7.
All records in a file must be able to be added, deleted, or
changed with a single command.
8.
Changes in how data is stored or retrieved should not
affect how the user accesses the data.
9.
The user's view of the data should be unaffected by its
actual form in files.
DEFINITION: A table is in the second normal form
if it is in the first normal form AND no column that
is not part of the primary key is dependant only a
portion of the primary key.

Remove any partial dependencies in a relation
THIRD NORMAL FORM
DEFINITION: A table is in the third normal form if
it is in the second normal form and there are no nonkey columns dependant on other non-key columns
that could not act as the primary key.

Ignore the key fields and check for any
dependencies between the other fields
BOYCE-CODD NORMAL FORM
DEFINITION: All attributes in a relation should be
dependant upon the key, the whole key and nothing
but the key


Within each of the candidate keys check for
dependencies
Only need to check for BCNF is when there is
more than one candidate key for a relation and
at least one of is composite
10. Constraints on user input should exist to maintain data
integrity.
11. A database design should allow for distribution of data
over several computer sites.
12. Data fields that affect the organization of the database
cannot be changed.
BIOGRAPHIES
DEPENDENCY
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If ‘X’ is a set of attributes within a
relation, then we say ‘A’ (an attribute
or set of attributes), is functionally
dependant on X, if and only if, for
every combination of X, there is only
one corresponding value of A
We write this as :
X -> A
2NF, 3NF and BCNF are concerned
with dependencies
2NF is concerned with partial
dependencies

Raymond ‘Ray’ Boyce
Ray Boyce grew up in New York, he went to college in Providence,
Rhode Island and got his PhD in Purdue. Together with Don Chamberlin
he developed SEQUEL. He died in 1974. PUBLICATION - Donald D.
Chamberlin, Raymond F. Boyce: SEQUEL: A Structured English Query
Language. SIGMOD Workshop, 1, 1974

Edgar ‘Ted’ Codd
Ted Codd is the father of the relational database. Born in 1923 in
Portland, UK, he got his PhD at the University of Michigan. He received
the 1981 Turing award for "his fundamental and continuing contributions
to the theory and practice of database management systems." He died in
2003. PUBLICATION - E. F. Codd: A Relational Model of Data for Large
Shared Data Banks. CACM 13 (6), 1970