Database Reference
In-Depth Information
A formal definition of division is as follows:
This definition has been recently refined in (the latest editions of ) Date's classic
text on database system [Date, 2004]. If you need additional information on the subject
matter, Date's text is recommended. However, since mastery of this is scarcely applicable
(if at all) at this level (in any event, division is a secondary operation), no further
discussion will take place.
7.4 Aliases, Renaming and the Relational
Assignment
In addition to the basic operations, three additional (advanced) operations defined on
relations are
•
Alias Operation
•
Rename Operation
•
Assignment Operation
7.4.1 The Alias Operation
Aliasing is giving an alternate name to a relation. The format is:
Example 7:
Aliasing is used when it is desirable to refer to different tuples in the same relation,
or when it is desirable to use a more convenient relation name in an application. Later
in the course, as you learn SQL (in an Oracle environment), you will see that aliases are
implemented as
synonyms
in Oracle.
