Database Reference
In-Depth Information
slowest processes within a database. Reducing R/W operations can improve database per-
formance.
Querying and reporting —
Querying or reporting operations in un-normalized database
is quite difficult. When first and last names are combined into a single field, then parsing
of the name field by last name becomes cumbersome.
Security control —
Normalization makes security more easier because the DBA can re-
strict table access to limited number of users. For example, within an staff directory, all
staff members may be permitted to view the name, home address, city, date of birth and
phone number of other staff members , but not their pay, perks, leaves and other informa-
tion.
5.5 DEFINITIONS OF NORMAL FORMS
There are six levels of normalization associated with six normal forms. A database's level
of normalization is, therefore, referred to as its normal form. The normal form is a meth-
od of measuring the level or depth to which a database has been normalized. The rules of
normalization are cumulative in nature. Each subsequent level depends upon normalization
steps taken in the previous normal form. A database must first be in the first normal (1NF)
form before it can be normalized to the second normal form(2NF), as we will see in the
following definitions and examples. The rules for normalizing tables in a database are ex-
plained as follows.
5.5.1 First Normal Form (1NF): Eliminating Repeating Data
Definition —
A relation is in first normal form if and only if every non-key attribute is func-
tionally dependent upon the primary key
First Normal Form (1NF) removes repeating groups such that all records in all tables can
be identified uniquely by a primary key in each table. All fields other than the primary key
must depend on the primary key. 1NF does the following:
1. Create a primary for each row of table.
2. Create a new table to move the repeating groups from the original table.
3. All fields other than the primary key must depend on the primary key, either directly or
indirectly.
4. All fields must contain a single value.
5. All values in each field must be of the same datatype.
