Databases Reference
In-Depth Information
ORCHESTRA relation
Orchestra
Music
Name
City
Country
Director
MUSICIAN relation
Musician
Musician
Annual
Orchestra
Number
Name
Instrument
Salary
Name
DEGREE relation
Musicia
n
Numbe
r
Degree
University
Year
COMPOSER relation
Composer
Date of
Name
Country
Birth
COMPOSITION relation
Composition
Name
Composer
Name
Year
RECORDING relation
Orchestr
a
Composition
Composer
Name
F IGURE 5.17
World Music Association relational
database
Name
Name
Year
Price
primary key of the COMPOSER relation, Composer Name, appear as a foreign key
in the COMPOSITION relation. Since composition names are unique only within
composers, the combination of Composition Name and Composer Name serves as
the compound primary key of the COMPOSITION relation.
The many-to-many relationship between orchestras and compositions indicates
which orchestras have recorded which compositions and which compositions have
been recorded by which orchestras. As a many-to-many relationship, it requires
that an additional relation be created. The primary key of this new RECORDING
relation has three attributes: Orchestra Name, Composition Name, and Composer
Name. Orchestra Name is the unique identifier of orchestras. The combination of
Composition Name and Composer Name is the unique identifier of compositions.
The combination of Orchestra Name, Composition Name, and Composer Name is
the unique identifier of the RECORDING relation. The Year and Price attributes are
intersection data in the RECORDING relation. If a particular orchestra could have
recorded a particular composition multiple times in different years (although we
assume that this is limited to once per year), Year must also be part of the primary
key of the RECORDING relation to provide uniqueness.
Search WWH ::
Custom Search