ITEC36 (Sir Noel) Flashcards
refers to the suppression
of details of data organization and
storage, and the highlighting of the
essential features for an improved
understanding of data.
Data Abstraction
a collection of concepts that can be used to
describe the structure of a database -
provides the necessary means to achieve
this abstraction.
Data Model
CATEGORIES OF DATA MODEL
- High-level or Conceptual Data
Models - Low-level or Physical Data Models
- Representational (or
implementation) Data Models
provide concepts that are close to the
way many users perceive data
Conceptual data models use concepts
such as entities, attributes, and
relationships.
High-level or Conceptual Data
Models
represents a real-world object or
concept
Entity
represents some property of
interest that further describes an entity
Attribute
among two or more entities
represents an association among the
entities,
Relationship
provide concepts that describe the
details of how data is stored on the
computer storage media, typically
magnetic disks.
Low-level or Physical Data
Models
provide concepts that may be easily
understood by end users but that are not
too far removed from the way data is
organized in computer storage
Representational (or
implementation) Data Models
represents the logical configuration of
all part of a relational database. It can
exist both as visual representation and
as a set of formulas known as integrity
constraints that govern a database
DATABASE SCHEMA
A displayed schema is called a what
Schema Diagram
Refers to the content of a database at
a moment in time.
It is also called the current set of
occurrences or instances in the
database.
DATABASE STATE or
SNAPSHOT
is property of
DBMS that helps you to change the
Database schema at one level of a
database system without requiring to
change the schema at the next higher
level. it also helps you to
keep data separated from all programs
that make use of it.
DATA INDEPENDENCE
is the capacity to change the
conceptual schema without having to
change external schemas or
application programs.
Logical data independence
is the capacity to change the internal
schema without having to change the
conceptual schema
Physical data independence
are the set of
statements, that are used to define and
manipulate a database.
Database Languages
has appropriate languages
and interfaces to express database
queries and updates.
DBMS
defines the statements to
implement the database schema.
DDL (Data Definition Language)
is a Database Management
System (DBMS) from Microsoft that combines
the relational Microsoft Jet Database Engine
with a graphical user interface and software
development tools.
Microsoft Access
stores information which
is called a database.
Microsoft Access
is an object that is used to
define and store data.
Tables
An object that provides a custom view
of data from one or more tables.
Query
is an object in a desktop database
designed primarily for data input or
display or for control of application
execution.
Form
is an object in desktop
databases designed for
formatting, calculating,
printing, and summarizing
selected data.
Report
This object is a structured definition
of one or more actions that you
want Access to perform in response
to a defined event.
Macro
is an object in desktop
databases containing custom
procedures that you code using
Visual Basic.
provide a more discrete
flow of actions and allow you to trap
errors.
Module
Every relation has some conditions
that must hold for it to be a valid
relation.
Relational Integrity Constraints.
three main relational
Integrity constraints
Key constraints
Domain constraints
Referential integrity constraints
An attribute that can uniquely identify
a tuple in a relation is called the key to
the table.
are also referred to as
Entity Constraints.
KEY CONSTRAINTS
can be violated
if an attribute value is not
appearing in the corresponding
domain, or it is not of the
appropriate data type.
DOMAIN CONSTRAINTS
specify that within
each tuple, and the value of each
attribute must be unique.
DOMAIN CONSTRAINTS
is an important attribute
of a relation which should be referred to
in other relationships.
foreign key
is an
arrangement of relation states in
such a manner that every relational
database state fulfills the integrity
constraints set on a relational
database schema.
RELATIONAL DATABASE SCHEMA
Defines the numerical attributes of
the relationship between two entities
or entity sets.
CARDINALITY
represents a
real-world object or
concept
Entity
Types of Attributes
Simple Attributes
Composite Attributes
Multi-valued Attributes
Derived Attributes
represents some
property of interest
that further describes
an entity
Attribute
are atomic values,
which cannot be
divided further.
they are also called
single-valued
attributes.
Simple attributes
are
made of more than
one simple attribute.
Composite
attributes
may
contain more than
one values.
Multi-value
attribute
are
the attributes that do
not exist in the physical
database, but their
values are derived from
other attributes present
in the database.
Derived attributes
a
single instance of an entity is
associated with a single instance of
another entity
One-to-One Relationships
a
single instance of an entity is
associated with more than one
instances of another entity
One-to-Many Relationships
more than one instances of an
entity is associated with a single
instance of another entity
Many-to-One Relationships
more than one instances of an
entity is associated with more than
one instances of another entity
Many-to-Many Relationships
provides operations that handle user
requests, offering a way to access and
manipulate the data that users store within
a database.
Data manipulation language (DML)
are set-oriented and specify what
data to retrieve than how to retrieve. Also
called declarative languages.
High Level or Non-procedural Languages
record-at-a-time; they specify how to retrieve
data and include constructs such as looping
Low Level or Procedural Languages
is a user interface which allows for
the ability to input queries to a database
without using the query language itself.
could be a web client, a
local client that runs on a desktop computer, or
even a mobile app.
DBMS INTERFACE
These interfaces present the user
with lists of options (called menus)
that lead the user through the
formulation of a request.
Menu-Based Interfaces for Web
Clients or Browsing.
displays a
form to each user.
Forms-Based Interfaces
typically displays a schema to
the user in diagrammatic form.
Graphical User Interfaces
These interfaces accept requests
written in English or some other
language and attempt to understand
them.
Natural Language Interfaces
The speech input is detected using a
library of predefined words and used to
set up the parameters that are supplied
to the queries.
For output, a similar conversion from
text or numbers into speech takes place
Speech Input and Output.
Parametric users, such as bank
tellers, often have a small set of
operations that they must perform
repeatedly
Interfaces for Parametric Users
it is a collective system of components that
comprise and regulates the group of data,
management and use of data which consist
of software, hardware, people, techniques of
handling database and the data also
DATABASE ENVIRONMENT
is used to load existing data
files—such as text files or sequential
files—into the database.
loading utility
creates a backup copy of
the database, usually by dumping the entire
database onto tape or other mass storage
medium.
backup
This utility can be used to reorganize a set
of database files into different file
organizations and create new access paths to
improve performance.
DATABASE STORAGE
REORGANIZATION
used in the design phase of database
systems
CASE TOOLS
this is another tool that can be quite useful
in large organizations
also called information repository
DATA DICTIONARY (or DATA
REPOSITORY) SYSTEM.
These systems provide an environment for
developing database applications and include
facilities that help in many facets of database
systems, including database design, GUI
development, querying and updating, and
application program development.
APPLICATION DEVELOPMENT
ENVIRONMENTS
combines everything into single system
including- DBMS software, hardware,
application programs and user interface
processing software.
CENTRALIZED DBMS
The client/server architecture was
developed to deal with computing
environments in which a large number of
PCs, workstations, file servers, printers, data
base servers, Web servers, e-mail servers,
and other software and equipment are
BASIC CLIENT/SERVER
ARCHITECTURES
The design of a DBMS depends on its
architecture. It can be centralized or
decentralized or hierarchical.
DATABASE ARCHITECTURE
the DBMS is the only
entity where the user directly sits on the
DBMS and uses it.
Any changes done here will directly be done
on the DBMS itself.
It does not provide handy tools for end-users.
Database designers and programmers normally
prefer to use the single-tier architecture.
TIER 1
the it
must have an application through which the
DBMS can be accessed.
Programmers use 2-tier architecture where
they access the DBMS by means of an
application.
Here the application tier is entirely
independent of the database in terms of
operation, design and programming
TIER 2
separates its tiers
from each other based on the
complexity of the users and how they
use the data present in the database.
It is most widely used architecture to
design a DBMS
TIER 3
At this tier, the database resides
along its query processing
languages.
We also have the relations that
define the date and their constraints
at this level.
Database (Data) Tier
At this tier reside the application
server and the programs that access
the database
Application (Middle) Tier
End-users operate on this tier, and
they know nothing about any
existence of the database beyond
this layer
User (Presentation) Tier
The relational data model was
introduced by who?
Edgar. F. Codd in 1969.
is the primary
data model, which is used widely
around the world for data storage and
processing. This model is simple, and it
has all the properties and capabilities
required to process data with storage
efficiency.
RELATIONAL DATA MODEL
represents records
rows
represent the attributes
column
A single row of a table, which contains
a single record for that relation is called
a what?
Tuple
A finite set of tuples in the relational
database system represents what
Relation Instance
describes the
relation’s name (table name), attributes,
and their names.
Relation Schema
Each row has one or more attributes, which can
identify the row in the relation (table)
uniquely.
Relation Key
Every attribute has some pre-defined
value scope,
Attribute Domain
is the original sets of atomic
values used to model data.
Domain
we mean that each
value in the domain is indivisible as far
as the relational model is concerned.
atomic value
