Java Reference
In-Depth Information
A relational table is in BCNF only if every column on which some of the columns are
fully functionally dependent is a candidate key. In other words, if the table has a
number of columns or groups of columns which could be used as the primary key
(so-called candidate keys), then to be in BCNF, the table must be in third normal form
for each of those candidate keys.
Normalization in Practice
Most databases can be considered to be adequately normalized when they are in the
fifth normal form. In the fifth normal form, a database has the following important
properties:
 
All records have the same number of fields.
 
All fields contain only a single data item.
 
There are no repeated fields.
 
All fields contain data related to the whole of the primary key.
 
The table does not contain two or more independent multivalued facts about the key.
 
The table does not contain two or more interdependent multivalued facts about the key.
Additional normal forms address situations that only apply in special situations. For
example, Boyce-Codd normal form requires that a table be in third normal form for
every column or group of columns which has the properties which could qualify it for
use as the primary key. In practice, the database designer will usually designate a
primary key, so the Boyce-Codd normal form will not be relevant, as other candidate
keys will not be used, so the third normal form is adequate.
High Level Language
Codd's Sub Language Rule (Rule 5) and his High Level Language Rule (Rule 7)
concern the availability of a language for use with the database. Descriptions of these
rules are restated here:
 
Sub Language Rule — An RDBMS must support a clearly defined data-manipulation language
that comprehensively supports data manipulation and definition, view definition, integrity
constraints, transactional boundaries, and authorization.
 
High Level Language Rule — An RDBMS must be able to retrieve relational data sets. It has to
be capable of insert, update, retrieve and delete data as a relational set.
The main features of this language are that it must have a linear syntax and must
support the following functions:
 
Data-definition operations (including view definitions)
 
Data update and retrieval operations
 
Data-integrity constraints
 
Transaction management
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