Some views might include derived or calculated data

users might view dates in the form (day/month/year) while others prefer (year/month/day).
Some views might include derived or calculated data. For example, a person’s age might
be calculated from his date of birth since storing his age would require it to be updated
each year.
Database Applications
A database application is an application program or a set of related programs that is
used to perform a series of activities on behalf of database users. These activities may
vary application to application according to the need. These activities may include.

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Data Base Management systems
Notes
Amity Directorate of Distance & Online Education
Insert: Add a new entry a new entry in the database.
Update: Modify data
Delete: Delete data form the database
Read: Read data from the database in a useful format on the screen or printer.
These database applications can be of various categories from stand-alone application
(only for a single user) to enterprise whose scope is the entire organization or enterprise.
The size of the database may also vary ranging from megabytes to several terabytes
depending upon the nature of the application.
Data Independence
The separation of data description from the application programs that uses the data is
called data independence. More simply, the ability to modify schema definitions at one level
without effecting a schema definition in the next higher level is called Data Independence.
Data independence can be defined at two levels: Logically and Physically. A well-designed
system maintains data independence both physically as well as logically. A brief overview
of both the levels are given here:
a) Logical Data Independence: Logical data independence refers to the immunity of
external schemas to changes in the conceptual schema. Changes to the conceptual
schema (adding/removing records, columns, or relationships) should be possible
without having to change existing external schemas or rewrite application programs.
The database can change and grow to reflect changes in reality without requiring the
user intervention or changes in the application programs or requests. For example, we
can delete a field from our database if the application program is not using that field.
Logical data independence is difficult to achieve than physical data independence
since programs are heavily dependent on the logical structure of the database.
b) Physical Data Independence: Physical data independence refers to the immunity
of the conceptual schema to changes in the internal schema. Changes to the internal
schema (using different storage structures or file organisations) should be possible
without having to change the conceptual or external schemas.
Database Language
To provide the various facilities to different types of users, a DBMS normally provides
one or more specialized programming languages often called Database Languages.
Database languages come in different forms. A language is needed to describe the database
to the DBMS as well as provide facilities for changing the database and for defining
and changing physical data structures. Another language is needed for manipulating