Database Sytems.docx by emathewjose

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Database Sytems.docx

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           Reliable Motors Database

               Mathew Jose


A database is a computerized record keeping system whose overall purpose is to maintain information and making
that information available on demand. Users of a database are given many facilitates such as adding new records to
a database, inserting new data, retrieving data from existing files, updating & deleting records as well. The
information can be anything that is deemed significant to the organization. In this case for reliable motors it is
information about clients, stock suppliers, customer orders and parts information all stored together. The facilities of
any system depend on the extent of the size of information and users accessing the database. The database has
been designed so that information may be accessed by multiple users at any given point of time. There are several
advantages of a database; compactness means that there is no need for voluminous paper files saving space and
natural resources. Speed means that the machine can retrieve and change data faster than a human can. This means
that search results required by a user such as “How many exhaust do we have in stock?” will be answered quickly.
Accuracy: - all the information that a user access will be easy to update and accurate information will be provided at
all times.

Redundancy means repetition of data in multiple instances when not required. This could result in inaccuracy of
data and wastage of storage space. For example a personnel application and an education-records application both
might need information about the department of t an employee. Using proper normalization techniques this can be
avoided and a database made more efficient. In the case reliable motors it is not necessary that all employees should
have access to all the information in the database. Hence security restriction can be applied to ensure that each
employee has access to enough information that is required by him/her to do their job efficiently and properly. The
input of data can also be validated so for example if a user tries to place an order and in the field for a phone
number the user enters alphabets, an error message will pop up and say that invalid characters have been used and
could request the user to try entering the correct value for that field. Integrity can also be maintained in a database
by careful planning and administration; for example if a dealer purchases 2 exhaust pipes then the database should
automatically update the quantity available for sale from x to x-2. This way data reports and stock counts can be
maintained accurately.

A database normally has entities which is Distinct “things” e.g. customers, products, students. Could be intangibles
such as HE courses, airline reservations, etc. Each entity has attributes, Relevant characteristics (or properties) of
entities. A customer will have a name, address, credit limit, etc. It could have a range of possible values. Each
attribute could be of various different types such as text, number, date, etc. A relationship is a recognised
connection between 2 (or more) entities.ANSI-SPARC stands for American National Standards Institute, Standards
Planning and Requirements Committee, is an abstract design standard for a Database Management System (DBMS),
first proposed in 1975. The ANSI-SPARC model is what modern commercial DBMS are based on. The ANSI-SPARC
model however never became a formal standard. The ANSI-SPAR consists of 3 levels

    •   Internal level
    •    Conceptual level
    •    External (view) level

This is a low level based representation of the entire database; it consists of many instances of each of many types of
internal records. “Internal record” is the ANSI-SPARC term for a stored record. The internal view effectively assumes
how an address is mapped to the physical storage. It describes how the data is actually stored in the database and
on the computer hardware.


This is a representation of the entire information content of the database. The conceptual view in essence is the
intended view of the data in its original form. This view may consist of multiple instances of each conceptual record.

For example it may consist of a collection of dealer records, supplier records and parts information. The conceptual
view is defined by the conceptual schema, which includes definitions of each of the various conceptual record types.
The conceptual level does not specify how the data is physically stored. The database administration takes place at
this level. It is in this level that data types, relationships, constraints and possible user operations against the data
are defined. Therefore the conceptual view is a view of the entire database content and the conceptual schema is
the definition of that view. It ultimate objective is to define how data is used, how data flows from one point to
another and what validation is required where.


The external level is the individual user level. These schemas describe logical views or approaches to the data in the
database of interest to particular user(s). A given user can be an administrator or a regular user. A programmer or
an administrator would use computer languages such as SQL, C+ and various other 4th generation languages to get
the required information however a user might use tools such as queries, or menu driven purpose specific interface
that meet the user requirements. A user's view of the database describes a part of the database that is relevant to a
particular user. It excludes irrelevant data as well as data which the user is not required to access.

All languages used have a sublanguage that consists of 2 sub ordinate languages. A Data Definition Language (DDA)
& Data Manipulation Language (DDL). The DDL consists of declarative constructs that are required to declare
database objects. The DML portion consists of executable statements that transfer information to and from the

Reliable Motors benefits from a database because No data is any longer “owned” by a single department; all data is
now a shared corporate resource. This means that all data can be accessed by multiple personnel at any time
without having to worry about data integrity and information being out of date. Security measures mean that the
data “view” can be specified for each employee therefore protecting information and providing user with enough
access to do their job properly.

 FK2 OrderID
 FK1 PartID
                                                       FK1 DealerID

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