In-depth notes and flashcards going over databases. Models, difference between information and data, scheme architecture and modelling, relationship models. Document and key value databases (Redis, Amazon DynamoDB), graph databases, DMS and DSMS, multi-user access control, backup and integrity mana...
Database Systems (COM1025)
https://labs.azure.com/virtualmachines
1) What is data? Data are raw, unanalysed facts.
▪ Data can be alphanumeric,
images and videos
▪ Data is the building blocks of
information
Data today has volume, velocity, variety – Big
Data
2) What is information? Information is data that has been processed into
a
meaningful form
Information is the base of knowledge and
decision-making.
3) What is knowledge? Knowledge is the capacity to use information for
making decisions.
4) What is a database? A collection of interrelated data, designed for an
organisation’s information needs.
▪ Access to accurate, relevant and
timely information is
critical for most organisations’ success.
5) What are the problems with file based ▪ Storage of duplicate or
databases compared to digital ones? redundant data
▪ Risk of data becoming
inconsistent
▪ Close coupling between
applications and data
▪ Difficult to integrate applications
▪ Difficult to provide concurrent
access to data
6) Why do we use databases? ▪ Data Independence – duplication,
inconsistency
, is minimised
▪ Data Persistence - sharable in a
secure way
▪ Data Abstraction - data models
key to database design
7) How are databases managed?
▪ Database Management System
(DBMS): define, create,
maintain, control access to database
▪ Application Programs: used to
interact with database
8) What is a model? What is a data model? A model is a simplified, miniature or abstract
representation of a real-world object or event
A data model is a collection of concepts for
representing complex real-world data in an
organisation in an abstract way.
▪ Objects/event (entities)
▪ Relationships (e.g. one-to-many,
many-to-many, one-to-one)
▪ Constraints
9) What are the benefits of data modelling? ▪ Provides an abstraction so no
need to be concerned with
, implementation
▪ Facilitates communication
between designer and user by
representing data in an
understandable way
▪ Provides different views to
different users
▪ An accurate data model is key to
good design
10) What is schema? The description of a database at a logical level
(usually in a formal language) supported by the
DBMS’s logical model.
, 11) What are the levels of a schema Physical Level
architecture? ▪ Storage structure of data
External Level
▪ Tailored to be viewed by a
particular category of users
▪ Hides data for security
Conceptual/Internal Level
▪ Defines the logical structure
▪ Bridge between the External
and Physical Levels
12) Why is database design important? ▪ A Database is designed to solve
problems presented by real use
cases
▪ Well-designed database gives
accurate information
▪ Badly designed database can
cause errors that lead to poor
decision making
▪ Data abstraction is key to good
design
▪ A database model consists of
different data models
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