Introduction to databases

A database is a
collection of organized
data, information and
records.

Database is information that a person needs
in his personal, business, social and religious
life and the power and purpose of
information is not only in collecting and
finding them but more importantly in using
them.

Structured database
It is also called the structured
data in which a record or
file of information arranged
in uniform format. These
databases are usually
storage of information with
similar entries such as a list
of persons born in a
country, a medical database
of patients’ data, an
inventory database of a
company and many others.
Free-form database
It is a loose collection of
information, such as
those you will find on the
World Wide Web. A
collection of your
documents in the
computer made from
several programs can be
considered as free-form
database.

Operational database
It is a dynamic database that
is used by any
organization in its day-to-
day operation. They are
used to collect data,
maintain, modify and
delete data.
Analytical database
It is a static database, where
data is rarely modified.
This database is often
used to store and track
historical data to make
long term projections and
analysis.

This model can be visualized as a
parent –child relationship wherein a
child may only have one parent but
parent can have several other
children.
Another way of looking at this
model is by visualizing an inverted
tree. The single table acts as the
root of the inverted tree and the
other tables act as branches.
To access the data from one of the
tables, one has to pass through the
root table. This model was popular
in the many IBM Information
Management Systems in the 1970s
using mainframe computers.

This model was developed to
address in part the problems of the
hierarchical model. As with
heirarchical model, it could be
visualized as an inverted tree;
however, this model allows many
inverted tress sharing branches but
are still part of the same database
structure.
As with the parent-child model, the
child is allowed to have multiple
parents. Unlike in the heirarchical
model access data begins from the
root table.
In the network model, it allows
access of data from any table . This
model was eventually replaced by
the relational database model.

Was developed by Dr. E. F. Codd of
IBM in the 1970s partly to solve the
problems of the earlier databse
models as well as finding a of making
database management less dependent
on any application.
The terms relations, attributes and
domains are used frequently in
relational database models.
A relation is a table with columns &
rows.
Attributes are thje names given to
each colunm of the relation.
Domain is the value with which the
attribute will take.
A relational database is essentially a
collection of tables, and if a databse is
a collection of tables, these tables are
simply called relations, hence, the
name.

Entity-relationship
Model
This model was
written by Peter
Chen in 1976.
This model is an
abstract and
coceptual
representation
of data.
Dimensional Model
Object-relational
model
Is a specialized adaption
using the relational
model that is used to
represent data in data
warehouses.
Data warehouses is
essentially storage of
all dgital data of a
company or
organization.
In this model, a single
large table of
information is used
using dimensions and
measures. Dimension
tells where, who and
what type while
measure would mean
quantity.
Is a model that
utilizes the
relationship
model as well as
the object-
oriented
programming
paradigm.
This model attempts
to bring together
database and
application
programming
closer together.

RDBMS is designed to creat,e,
maintain, manipulate,, modify and
delete information in a relational
database.
As previously mentioned, moderm
database utilize the relational
database model and many of
today’s software caters to this type
of structured database.

Create a database
Information storage
Information retrieval
Information management
Information analysis
Print and share information

It is a number or
value found and
stored in the
database. Data is
static because it
remains the same
until it is modified
by a process.

It is a data that has been
processed thereby
making it. Relevant and
meaningful to the
person viewing it..
Information is dynamic
because it changes
relative to the data
stored in the database
and it could be
processed in many ways.

It is used to represent a
value that is unknown or
missing. A null value is
niether a zero nor a
blank.

It is the main structure in
the relational database.
It is composed of
attributes (fields) and
domain (records). A
table almost always
represents a subject that
can be an object
(person, place, or thing)
or an event.

It is an organized
collection of data about
an entity. As an example,
for a bookstore, a file
called “Branch” can
contain all the data
about a particular
bookstore branch.

It refers to a specific person, place,
thing, or event. Record is also
known as the “tuple” in the
relational database terminology. It
pertains to structure in the
database table representing a
unique instance of a subject.

It is the smallest
structure of a data from
a larger database
structure in a relational
database. A field can
store data in a database
and represent a
character opf the subject
to which database table
it resides.

It is also known as a
virtual table . It is called
a virtual table since it
does not hold data on its
own; rather it gets data
from the table which it is
based. And since it
comes from other table
it is composed of several
fields coming from one
or more data.

These are fields that serve
specific purposes within a
table. There are two types
of keys, the primary key
and the foriegn key .
The Primary key is a field
that uniquely identifies a
record in the table.
The Foreign key is a special
field that establishes a
relationship between two
tables.

They exist when
two or more
tables have
connection or
association .

Primary key
Foreign key
Linking table is a table that
establishes a connection between
two or more tables

When two or more tables are
related, there exist between them
a specific type of relationship and
there are three types of possible
relationships.

This relationship
exist between tables
when only one
record of the first
table is related to
only one record to a
second table, and
only one record of
the second table is
related to only one
record to the first
table.

This relationship exist
between tables when one
record of the first table can
be related to one or more
records to a second table,
but only one record from
the second table can be
related to a single record in
the first table.
This relationship is the most
common relationship that
exist between tables and
helps to reduce or eliminate
duplicate and redundant
data.

This relationship exists
between tables when
one record of the first
table can be related to
one or more records to a
second table and one
record drom the second
table can be related to
one or more records to
the first table.
The connection between
the two tables will be
difficult to establish and
will resullt to redundant
data in one of the tables.

 Define the purpose of your database. Consider the questins or
queries you may want to answer about the stored data.
 Determine the tables that you need in the databse.
 Determine the fields that you need in the database.
 Identify unique fields values that you will allow Access to
connect information stored in a separate table.
 Determine the relationships between tables. A relationship
works by matching data in the key fields which is usually a
field with the same name in both tables.
 Test the design by entering the sample data. Check that you
can run a query on the database and get the information you
want.

 Modify data is easy. Changes to the value of one field within
the table should not affect the values of the fields in the
table.
 Retrieving information is easy. Extracting desired information
from tables with well defined relationships should make
accessing and retrieving data a lot faster.
 Developing and building user application is easy. Data
manipulation would be the main focus of programming and
not solving the problems associated with a poorly designed
database.
 Maintaining the structure is easy. Changes made to any
table. Or columns should not affect other tables or columns.
 Adding and deleting data is easy.

A spreadsheet is very
powerful if used properly;
however, it is designed for a
purpose and always will
find a purpose within any
business or organization .
Spreadsheets do not make
good relational database,
because if you really need
to acquire and collect, store
and maintain, view and
analyze, print and share
data then you need a tool
that will truly suit in
designing a real database.

Secondly, you should also
get away from the
“spreadsheet view”
mentality. Spreadsheets
may seem to offer a good
means to view data;
however, a database
program may not be able
to produce a report of a
spreadsheet layout.
A database presentation
may not be the same as
that of a spreadheet but it
could be just as clear.

Introduction to databases

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